Make the MR/issue templates look a bit nicer

What does this MR do?

This MR makes some opinionated changes to the GitLab issue and merge request templates in hopes of making them look a bit nicer.

Bug report template

Feature request template

(For the merge request template, you can just look at this MR)

Contribution Guidelines

By submitting this merge request, you agree to follow our Contribution Guidelines

• I agree to follow this project's Contribution Guidelines
• I have made sure to test this merge request

changed the description

changed the description

approved this merge request

mentioned in issue CenTdemeern1/Sharkey#2 (closed)

mentioned in issue CenTdemeern1/Sharkey#1 (closed)

approved this merge request

mentioned in commit b48ae3e9

merged