DOC: Update Git commit message guidelines

See also confirm/python-libraries/tools#19
3 jobs for master in 2 minutes and 29 seconds (queued for 66 minutes and 12 seconds)
Name Stage Failure
failed
Test JavaScript & CSS Test
Using docker image sha256:3d3f41722daf1a77c34d6eade6676bbffa2d6a2a21095de2ab0c427a5c942fc9 for node:15 with digest node@sha256:608bba799613b1ebf754034ae008849ba51e88b23271412427b76d60ae0d0627 ...
Preparing environment
Running on runner-28e6b4gy-project-242-concurrent-0 via dev1.pvt.confirm.ch...
Getting source from Git repository
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/confirm/development-guidelines/.git/
fatal: unable to access 'https://git.confirm.ch/confirm/development-guidelines.git/': Failed to connect to git.confirm.ch port 443: Operation timed out
Cleaning up file based variables
ERROR: Job failed: exit code 1