Move list of ignored commits to root

This was initially added [here][1] but wasn't quite in the right place
to have the intended effect.

Let's move it up to the root of the project.

[1]: f515663640

.git-blame-ignore-revs

@@ -0,0 +1,5 @@
+# Run this command to always ignore formatting commits in `git blame`
+# git config blame.ignoreRevsFile .git-blame-ignore-revs
+
+# Formatted all code using Prettier instead of tsfmt
+ebcdf8ad0bb5bcb3efa679211709671716b892ba