docs: include more Git project-specific pages

Now that they are clearly labeled as such, let's augment the list of
"manual pages" that concern themselves with information only relevant
for contributors to the Git project itself.

This closes git#1938,
git#1939 and
git#1961.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

content/community/_index.html

@@ -101,7 +101,7 @@ <h2 id="git-rev-news"><a class="anchor" href="#git-rev-news"></a> Newsletter </h
   <h2 id="contributing"><a class="anchor" href="#contributing"></a> Contributing to Git </h2>
 
   <p>
-    The <a href="https://github.com/git/git/tree/master/Documentation">Documentation directory</a> in the Git source code has several files of interest to developers who are looking to help contribute. After reading the <a href="https://github.com/git/git/blob/master/Documentation/CodingGuidelines">coding guidelines</a> and <a href="https://github.com/git/git/blob/master/CODE_OF_CONDUCT.md">code of conduct</a>, you can learn <a href="{{< relurl "docs/SubmittingPatches" >}}">how to submit patches</a>. If you are just starting out, you can read the <a href="{{< relurl "docs/MyFirstContribution" >}}">My First Contribution tutorial</a>. For those looking to get more deeply involved, there is a <a href="https://github.com/git/git/blob/master/Documentation/howto/maintain-git.txt">howto for Git maintainers</a>.
+    The <a href="https://github.com/git/git/tree/master/Documentation">Documentation directory</a> in the Git source code has several files of interest to developers who are looking to help contribute. After reading the <a href="{{ relURL "docs/CodingGuidelines" }}">coding guidelines</a> and <a href="https://github.com/git/git/blob/master/CODE_OF_CONDUCT.md">code of conduct</a>, you can learn <a href="{{< relurl "docs/SubmittingPatches" >}}">how to submit patches</a>. If you are just starting out, you can read the <a href="{{< relurl "docs/MyFirstContribution" >}}">My First Contribution tutorial</a>. For those looking to get more deeply involved, there is a <a href="https://github.com/git/git/blob/master/Documentation/howto/maintain-git.txt">howto for Git maintainers</a>.
   </p>
 
   <p>

data/docs_extra.yml

@@ -1,6 +1,9 @@
 ---
 git_project_specific:
+  - BreakingChanges
+  - CodingGuidelines
   - MyFirstContribution
   - MyFirstObjectWalk
+  - ReviewingGuidelines
   - SubmittingPatches
 ---