Add issue and PR templates

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -0,0 +1,62 @@
+name: Bug Report
+description: Report a bug
+title: "<title>"
+labels: "t: bug"
+body:
+  - type: checkboxes
+    attributes:
+      label: Is there an existing issue for this?
+      description: Please search to see if an issue already exists for the bug you encountered.
+      options:
+      - label: I have searched the existing issues for a bug report that matches the one I want to file, without success.
+        required: true
+  - type: checkboxes
+    attributes:
+      label: Did you read the documentation and troubleshoot guide?
+      description: Please read [README.md](https://github.com/sagemath/sage/blob/develop/README.md) and [the Troubleshooting section in the Installation Guide](https://doc.sagemath.org/html/en/installation/troubles.html).
+      options:
+      - label: I have read the documentation and troubleshoot guide
+        required: true
+  - type: textarea
+    attributes:
+      label: Environment
+      description: |
+        examples:
+          - **OS**: Ubuntu 20.04
+          - Sage Version: 9.2
+      value: |
+          - **OS**:
+          - **Sage Version**: 
+      render: markdown
+    validations:
+      required: true
+  - type: textarea
+    attributes:
+      label: Steps To Reproduce
+      description: Steps to reproduce the behavior.
+      placeholder: |
+        1. In this environment...
+        2. With this config...
+        3. Run '...'
+        4. See error...
+    validations:
+      required: false
+  - type: textarea
+    attributes:
+      label: Expected Behavior
+      description: A clear and concise description of what you expected to happen.
+    validations:
+      required: true
+  - type: textarea
+    attributes:
+      label: Actual Behavior
+      description: A clear description of what actually happens.
+    validations:
+      required: true
+  - type: textarea
+    attributes:
+      label: Additional Information
+      description: |
+        Links? References? Anything that will give us more context about the issue you are encountering!
+    validations:
+      required: false

.github/ISSUE_TEMPLATE/failure_building_from_source.yml

@@ -0,0 +1,67 @@
+name: Failure building from source
+description: Use this template when reporting a build failure
+title: "<title>"
+labels: ['c: build', 't: bug']
+assignees: []
+body:
+  - type: checkboxes
+    attributes:
+      label: Is there an existing issue for this?
+      description: Please search to see if an issue already exists for the bug you encountered.
+      options:
+      - label: I have searched the existing issues for a bug report that matches the one I want to file, without success.
+        required: true
+  - type: checkboxes
+    attributes:
+      label: Did you read the documentation and troubleshoot guide?
+      description: Please read [README.md](https://github.com/sagemath/sage/blob/develop/README.md) and [the Troubleshooting sectionin the Installation Guide](https://doc.sagemath.org/html/en/installation/troubles.html).
+      options:
+      - label: I have read the documentation and troubleshoot guide
+        required: true
+  - type: textarea
+    attributes:
+      label: Environment
+      description: |
+        examples:
+          - **OS**: Ubuntu 20.04
+          - Sage Version: 9.2
+      value: |
+          - **OS**:
+          - **Sage Version**: 
+      render: markdown
+    validations:
+      required: true
+  - type: textarea
+    attributes:
+      label: Steps To Reproduce
+      description: Steps to reproduce the behavior.
+      placeholder: |
+        1. In this environment...
+        2. With this config...
+        3. Run '...'
+        4. See error...
+    validations:
+      required: false
+  - type: textarea
+    attributes:
+      label: Config log
+      description: |
+        Please attach `config.log`.
+        Tip: You can attach log files by clicking this area to highlight it and then dragging files in.
+    validations:
+      required: true
+  - type: textarea
+    attributes:
+      label: Package logs
+      description: |
+        Please attach ̀`logs/pkgs/SPKG.log` for failing packages.
+        Tip: You can attach log files by clicking this area to highlight it and then dragging files in.
+    validations:
+      required: false
+  - type: textarea
+    attributes:
+      label: Additional Information
+      description: |
+        Links? References? Anything that will give us more context about the issue you are encountering!
+    validations:
+      required: false

.github/ISSUE_TEMPLATE/feature_report.yml

@@ -0,0 +1,36 @@
+name: Feature Request
+description: Suggest an idea
+title: "<title>"
+labels: "t: enhancement"
+body:
+  - type: checkboxes
+    attributes:
+      label: Is there an existing issue for this?
+      description: Please search to see if an issue already exists for the bug you encountered.
+      options:
+      - label: I have searched the existing issues for a bug report that matches the one I want to file, without success.
+        required: true
+  - type: textarea
+    attributes:
+      label: Problem Description
+      description: Please add a clear and concise description of the problem you are seeking to solve with this feature request.
+    validations:
+      required: true
+  - type: textarea
+    attributes:
+      label: Proposed Solution
+      description: Describe the solution you'd like in a clear and concise manner.
+    validations:
+      required: true
+  - type: textarea
+    attributes:
+      label: Alternatives Considered
+      description: A clear and concise description of any alternative solutions or features you've considered.
+    validations:
+      required: true
+  - type: textarea
+    attributes:
+      label: Additional Information
+      description: Add any other context about the problem here.
+    validations:
+      required: false

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,4 +1,23 @@
-Thanks for contributing to Sage! Detailed instructions to be added shortly.
+### 📚 Description
+
+<!-- Describe your changes in detail -->
+<!-- Why is this change required? What problem does it solve? -->
+<!-- If it resolves an open issue, please link to the issue here. For example "Closes #1337" -->
+
+### 📝 Checklist
+
+<!-- Put an `x` in all the boxes that apply. -->
+<!-- If your change requires a documentation PR, please link it appropriately -->
+<!-- If you're unsure about any of these, don't hesitate to ask. We're here to help! -->
+
+- [ ] I have linked an issue or discussion.
+- [ ] I have created tests covering the changes.
+- [ ] I have updated the documentation accordingly.
+
+### ⌛ Dependencies
+<!-- List all open pull requests that this PR logically depends on -->
+<!--
+- #xyz: short description why this is a dependency
+- #abc: ...
+-->
 
-Please make sure to also have a look at our
-[Code Style Conventions](https://doc.sagemath.org/html/en/developer/coding_basics.html).