add a .git-blame-ignore-revs file

This cleans up 'git blame' by automatically skipping commits that
just reformatted code using clang-format. The name of the ignore-
file isn't standard, but it seems to be the convention.

To use this, you'll have to adapt your git config like so:

git config --global blame.ignoreRevsFile .git-blame-ignore-revs
git config --global blame.markIgnoredLines true

The first config enables the usage of the ignore file by default,
the second one marks blame-lines with a '?' if they skipped one
or more commits.

.git-blame-ignore-revs

@@ -0,0 +1,14 @@
+# [clang-format] initial apply to the code base
+3f87e1eef7dbfe231d833ffbf06f7a85b070b600
+
+# [clang-format] upgrade v17
+fe7a2a1d850ae02934ea04d25fa214c825442535
+
+# [clang-format] Add DEPRECATED macros
+697fec3aa0de3b9c1683206c99683a13c115ff9f
+
+# [clang-format] AllowShortFunctionsOnASingleLine
+62eeefff1c59f8cc977027d9260c07cf518f6377
+
+# [clang-format] AllowShortBlocksOnASingleLine
+de48a2eb6d2d77e104044da84c2fb7df5c08d65a