Style: updates a git commit template

A nice readable git history is always appreciated. By nudging people in
using our template, we hope to achieve that. Through the inclusion of a
CONTRIBUTING.md we hope to make that easier.

 - Fixes #8845

CONTRIBUTING.md

+# Contributed Files
+
+## Commit Template
+
+To install our commit template, use following command (use --global to use it in your global .gitconfig):
+
+    git config [--global] commit.template "~/path_to_leap_platform/contrib/leap-commit-template"
+
+## Signing commits
+
+We very much appreciate signed commits, you can stop forgetting it like this:
+
+    git config [--global] commit.gpgSign

contrib/README.md

-# Contributed Files
-
-## Commit Template
-
-to install this commit template, use following cmd (use --global to use it in your global .gitconfig):
-
-    git config [--global] commit.template "~/path_to_leap_platform/contrib/commit-template.txt"
-
-

contrib/commit-template.txt

-#[bug|feat|docs|style|refactor|test|pkg|i18n]
-
-#- Tested: [local singlenode|local multinode|citest|unstable.bitmask.net]
-#- Resolves: #XYZ
-#- Related: #XYZ
-#- Documentation: #XYZ
-#- Releases: XYZ

contrib/leap-commit-template

+# Bug|Feat|CI|Docs|Style|Tests|I18n|Vagrant|Lint: [style: https://github.com/m1foley/fit-commit]
+
+
+# [Story about your commit.]
+
+# Use one or more of these things:
+# - Fixes|Closes #3210
+# - Related: #1234
+
+#example:
+#    
+#   Bug: fix apache systemd insanity
+#    
+#   Apache2 systemd autorestart was failing because of #2314432
+#   and it was caused by a gremlin that was entering through a wormhole
+#   caused by #985843, so this commit resolves this wormhole
+#    
+#    # Use one of these things:
+#    [- Fixes|Closes #5234]
+#    [- Related: #1234]