chore: hard code links in the pull request template

[EricRibeiro]

Changes

• Replace relative links with their full path equivalent

Relative links do not work in pull requests. Support was requested here, but the feature was never implemented. More information can be found here.

Checklist

• [x] Read the contribution guide and accept the code of conduct
• [x] Documentation (updated or not needed)
• [x] Tests (added, updated or not needed)