Improve link to CI solutions

Update docs/content/doc/advanced/ci-cd.en-us.md

Co-Authored-By: Lauris BH <[email protected]>

Author: camlafit

docs/content/doc/advanced/ci-cd.en-us.md

@@ -22,11 +22,11 @@ NOTE: These tools are not endorsed by Gitea. They are listed here for convenienc
 CI/CD solutions that have integration with Gitea. Following list is not complete,
 the purpose is to give a starting point to integrate a CI/CD process with Your Gitea instance.
 
- - Drone : https://drone.io
- - Jenkins : https://plugins.jenkins.io/gitea
- - Agolia :  https://agola.io
- - Buildkite : https://buildkite.com and https://github.com/techknowlogick/gitea-buildkite-connector
+ - [Drone](https://drone.io)
+ - [Jenkins](https://plugins.jenkins.io/gitea)
+ - [Agolia](https://agola.io)
+ - [Buildkite](https://buildkite.com) with [Gitea connector](https://github.com/techknowlogick/gitea-buildkite-connector)
 
 
 Others CI/CD solutions that partially can be integrated with Gitea:
- - concourse-ci : https://www.concourse-ci.org and https://discuss.concourse-ci.org/t/concourse-ci-and-gitea-oauth/1475
+ - [Concourse](https://www.concourse-ci.org), see more informations at [Concourse community forum](https://discuss.concourse-ci.org/t/concourse-ci-and-gitea-oauth/1475)