Make link from the PR template absolute to website checklist

[nsryan2]

Summary of changes

This PR closes #320 by making the link from the PR template absolute to the PR Review Checklist on the website instead of relative. The relative link wasn't working from actual PRs (you can see in this PR how the relative link wasn't working).

Requesting @RhysMacMillan so he can practice reviewing a PR.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

Associated Issues and PRs

• Issue: Update PR Review checklist link in the PR template #320

Associated Developers

• Dev: @RhysMacMillan

Checklist for Reviewers

Reviewers should use this link to get to the
Review Checklist before they begin their review.

[RhysMacMillan]

This looks great! The link is correctly changed and works as intended.

[nsryan2]

Great, you can merge when you're ready @RhysMacMillan