Add simple github PR template

Users tend to open pull request without notice that patches should be
sent to [email protected]

This template should give them a basic hint how to send patches for
review directly when they open a new PR.

Signed-off-by: Petr Lautrbach <[email protected]>
Acked-by: Stephen Smalley <[email protected]>

Author: bachradsusi

.github/pull_request_template.md

@@ -0,0 +1,15 @@
+Please read [CONTRIBUTING.md](https://github.com/SELinuxProject/selinux/blob/main/CONTRIBUTING.md)
+
+## Contributing Code
+
+Post the patch for the review to the
+[SELinux mailing list](https://lore.kernel.org/selinux) at
+[[email protected]](mailto:[email protected]).
+
+When preparing patches, please follow these guidelines:
+
+-   Patches should apply with git am
+-   Must apply against HEAD of the main branch
+-   Separate large patches into logical patches
+-   Patch descriptions must end with your "Signed-off-by" line. This means your
+    code meets the Developer's certificate of origin, see below.