CONTRIBUTING: add more topic headers

Add the subsections of "Submitting Pull Requests" and the missing
"Unit Tests" header in CONTRIBUTING_GO.md.

Signed-off-by: Paul Holzinger <[email protected]>

Author: Luap99

CONTRIBUTING.md

@@ -32,6 +32,10 @@ However, most of the things here listed are very generic and apply when contribu
 
 * [Reporting Issues](#reporting-issues)
 * [Submitting Pull Requests](#submitting-pull-requests)
+  * [Describe your Changes in Commit Messages](#describe-your-changes-in-commit-messages)
+  * [Sign your PRs](#sign-your-prs)
+  * [Code review](#code-review)
+  * [Rebasing](#rebasing)
 * [Find bad changes with git bisect](#find-bad-changes-with-git-bisect)
 
 ## Reporting Issues

CONTRIBUTING_GO.md

@@ -13,6 +13,7 @@ At present, this means the following repositories:
 
 ## Topics
 
+* [Unit Tests](#unit-tests)
 * [Go Dependency updates](#go-dependency-updates)
 * [Testing changes in a dependent repository](#testing-changes-in-a-dependent-repository)
 * [git bisect a change in a Go dependency](#git-bisect-a-change-in-a-go-dependency)