Rename CONTRIBUTING to CONTRIBUTING.rst for Gitlab formatting preview.

Rename occurences of the file through the documentation.

Signed-off-by: Thomas Citharel <tcit@tcit.fr>
8 jobs for rename-contributing in 4 minutes and 28 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Review
manual #7872
funkwhale-review allowed to fail manual
review_docs
manual #7870
funkwhale-review allowed to fail manual
review_front
manual #7873
funkwhale-review allowed to fail manual
stop_docs_review
manual #7871
funkwhale-review allowed to fail manual
stop_front_review
 
  Lint
passed #7874
black

00:00:27

passed #7875
flake8

00:00:25

 
  Test
passed #7876
docker
test_api

00:03:46

passed #7877
docker
test_front

00:03:58