[folks] Rename HACKING.md to CONTRIBUTING.md

[Niels De Graef <nielsdg src gnome org>]

commit 6049e578ef1fc7b36ab9e4c9d7d6246d59621b47
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Sun Jun 7 14:25:33 2020 +0200

    Rename HACKING.md to CONTRIBUTING.md
    
    GitLab picks up on this filename to show some extra UI, so let's just
    use it instead of HACKING.

 HACKING.md => CONTRIBUTIONS.md | 0
 README.md                      | 3 ++-
 tests/README                   | 1 -
 3 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/HACKING.md b/CONTRIBUTIONS.md
similarity index 100%
rename from HACKING.md
rename to CONTRIBUTIONS.md
diff --git a/README.md b/README.md
index ef53aef2..6400e7c1 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,8 @@ Please try to add reproducible steps and the relevant version of libfolks.
 
 If you want to contribute functionality or bug fixes, please open a Merge
 Request (MR). For more info on how to do this, see GitLab's [help pages on
-MR's]. Please also follow our coding conventions, as described in HACKING.md
+MR's]. Please also follow our coding conventions, as described in
+CONTRIBUTIONS.md
 
 If libfolks is not translated in your language or you believe that the current
 translation has errors, you can join one of the various translation teams in