Add a how to get involved section to developer frontpage

Much more can be done to help this page, but it's a start.

Reviewed-by: Daniel Gustafsson and Jonathan Katz

Author: mhagander

templates/pages/developer.html

@@ -21,6 +21,16 @@ <h2>What will you find here?</h2>
 necessarily available in the release version of PostgreSQL - it may not yet even be in the development version.
 </p>
 
+<h2>How to get involved</h2>
+<p>
+  A few resorces to help you get involved in PostgreSQL development are:
+</p>
+<ul>
+  <li>Read the <a href="https://wiki.postgresql.org/wiki/Developer_FAQ#How_do_I_get_involved_in_PostgreSQL_development.3F">Developer FAQ</a>.</li>
+  <li>Read the <a href="https://www.postgresql.org/list/pgsql-hackers/">pgsql-hackers archives</a> about topics, and optionally <a href="https://lists.postgresql.org/">subscribe</a> to the list.</li>
+  <li>Join the <a rel="nofollow" href="https://discord.gg/bx2G9KWyrY">PostgreSQL Hacking Discord</a>.</li>
+</ul>
+
 <h2>What is a CommitFest?</h2>
 
 A <a href="https://commitfest.postgresql.org">CommitFest</a> is a period during