move CONTRIBUTING.md to rustc-dev-guide

Author: mark-i-m

src/SUMMARY.md

@@ -4,8 +4,7 @@
 
 ---
 
-- [Part 1: Building, debugging, and contributing to Rustc](./part-1-intro.md)
-    - [About the compiler team](./compiler-team.md)
+- [Part 1: Building and debugging Rustc](./part-1-intro.md)
     - [How to Build and Run the Compiler](./building/how-to-build-and-run.md)
         - [Suggested Workflows](./building/suggested.md)
         - [Bootstrapping](./building/bootstrapping.md)
@@ -16,24 +15,26 @@
         - [Running tests](./tests/running.md)
         - [Adding new tests](./tests/adding.md)
         - [Using `compiletest` + commands to control test execution](./compiletest.md)
-    - [Walkthrough: a typical contribution](./walkthrough.md)
-    - [Bug Fix Procedure](./bug-fix-procedure.md)
-    - [Implementing new features](./implementing_new_features.md)
-    - [Stability attributes](./stability.md)
-    - [Stabilizing Features](./stabilization_guide.md)
     - [Debugging the Compiler](./compiler-debugging.md)
     - [Profiling the compiler](./profiling.md)
         - [with the linux perf tool](./profiling/with_perf.md)
-    - [Coding conventions](./conventions.md)
     - [crates.io Dependencies](./crates-io.md)
     - [Errors and Lints](diagnostics.md)
         - [`LintStore`](./diagnostics/lintstore.md)
         - [Diagnostic Codes](./diagnostics/diagnostic-codes.md)
+- [Part 1.5: Contributing to Rust](./contributing.md)
+    - [About the compiler team](./compiler-team.md)
+    - [Walkthrough: a typical contribution](./walkthrough.md)
+    - [Bug Fix Procedure](./bug-fix-procedure.md)
+    - [Implementing new features](./implementing_new_features.md)
+    - [Stability attributes](./stability.md)
+    - [Stabilizing Features](./stabilization_guide.md)
     - [Notification groups](notification-groups/about.md)
         - ["Cleanup Crew"](notification-groups/cleanup-crew.md)
         - [LLVM](notification-groups/llvm.md)
         - [Windows](notification-groups/windows.md)
         - [ARM](notification-groups/arm.md)
+    - [Coding conventions](./conventions.md)
     - [Licenses](./licenses.md)
 - [Part 2: High-level Compiler Architecture](./part-2-intro.md)
     - [Overview of the Compiler](./overview.md)