Add a .git-blame-ignore-revs file (#77357)

Hello!

@malfet @janeyx99 This PR adds a [`.git-blame-ignore-revs`](https://docs.github.com/en/repositories/working-with-files/using-files/viewing-a-file#ignore-commits-in-the-blame-view) file to the PyTorch repo, to hide a few big noisy commits which currently make the GitHub blame view more difficult to use. See this blog post: https://github.blog/changelog/2022-03-24-ignore-commits-in-the-blame-view-beta/
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77357
Approved by: https://github.com/seemethere

.git-blame-ignore-revs

@@ -0,0 +1,24 @@
+# 2020-11-12 Enabled ShellCheck on `.jenkins/pytorch`
+65d5004b09fd8d5deac173a3aaa259f46eaa0d67
+# 2021-01-20 Replaced `   ` with `...` in many doctests
+c147aa306c6386a753fdff24b48d04e803070a63
+# 2021-03-05 Removed all trailing whitespace
+8c798e062216278673a75bac0848ea69a8bd3f03
+# 2021-03-30 Normalized trailing newlines
+5bcbbf537327f6e8328289c25a3a453a2444d984
+# 2021-03-31 Autogenerated Markdown ToCs
+a74b10def961ab090385f291ee06e66db99c1a2f
+# 2021-04-02 Enabled more ShellCheck warnings
+09670c7d43b9abce862a6bf71d8cc89e64764bdb
+# 2021-04-08 Removed all non-breaking spaces
+cc11aaaa60aadf28e3ec278bce26a42c1cd68a4f
+# 2021-04-13 Expanded many wildcard imports
+4753100a3baa96273204c361c8452afb7b59836f
+# 2021-04-19 Removed all unqualified `noqa`
+e3900d2ba5c9f91a24a9ce34520794c8366d5c54
+# 2021-04-21 Removed all unqualified `type: ignore`
+75024e228ca441290b6a1c2e564300ad507d7af6
+# 2021-05-14 Removed all versionless Python shebangs
+2e26976ad3b06ce95dd6afccfdbe124802edf28f
+# 2021-06-07 Strictly typed everything in `.github` and `tools`
+737d920b21db9b4292d056ee1329945990656304