[gedit] contributing: add *.md file extension

[Sébastien Wilmet <swilmet src gnome org>]

commit f4f6f4f7c72a7ce275b48538986a9119182073b8
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Mon Aug 26 11:27:27 2019 +0200

    contributing: add *.md file extension
    
    The file is now fully in Markdown.

 CONTRIBUTING => CONTRIBUTING.md           | 0
 README.md                                 | 2 +-
 docs/gedit-development-getting-started.md | 4 +++-
 3 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/CONTRIBUTING b/CONTRIBUTING.md
similarity index 100%
rename from CONTRIBUTING
rename to CONTRIBUTING.md
diff --git a/README.md b/README.md
index 8643b4b09..b8117979e 100644
--- a/README.md
+++ b/README.md
@@ -59,4 +59,4 @@ Contributions
 gedit development relies on voluntary contributions and everyone is invited
 to help.
 
-See the file `CONTRIBUTING` for more information.
+See the file `CONTRIBUTING.md` for more information.
diff --git a/docs/gedit-development-getting-started.md b/docs/gedit-development-getting-started.md
index 789834fe1..158ca2696 100644
--- a/docs/gedit-development-getting-started.md
+++ b/docs/gedit-development-getting-started.md
@@ -80,7 +80,9 @@ See the [Newcomers](https://wiki.gnome.org/Newcomers/) page to start
 contributing to GNOME in general.
 
 To know how to contribute to gedit specifically, read the `README.md` and
-`CONTRIBUTING` files present in the Git repository.
+`CONTRIBUTING.md` files present in the Git repository (and then you'll see that
+the `CONTRIBUTING.md` file refers to this file, but please don't end up in an
+infinite reading loop).
 
 To find something interesting to do, […]. TODO: provide list of easy tasks in
 gedit itself.