Add .git-blame-ignore-revs

[whabanks]

Summary | Résumé

This PR adds .git-blame-ignore-revs to the project. This lets us to filter out specified commits when using git blame, e.g. bulk formatting and other changes that do not affect functionality.

To ignore a commit, just add the commit SHA to .git-blame-ignore-revs

Test instructions | Instructions pour tester la modification

1. Open .git-blame-ignore-revs and open one of the links to an ignored commit.
2. Open a file that the ignored commit changed and run git blame.
3. Note that the ignored commits are not present and the commit previous is shown instead.

After this PR is merged

• Repeat the above steps but open the file on the Github website and open the blame tool
• The excluded commits are not present on the web version
• Appending a ~ to the commit SHA in the URL shows the ignored commits