Add clang-format rule for Filecoin System Test Matrix (#501)

Signed-off-by: Alexey-N-Chernyshov <[email protected]>

Author: Alexey-N-Chernyshov

.clang-format

@@ -8,3 +8,8 @@ BinPackArguments: false
 BinPackParameters: false
 AllowShortFunctionsOnASingleLine: Empty
 IncludeBlocks: Preserve
+
+# Comment pragma for Filecoin System Test Matrix (https://github.com/filecoin-project/system-test-matrix)
+# Comment format is '//stm:tags=...;ignore=...' with no whitespace. This is a go convention for comments that are not
+# meant to be read by humans and must not be changed by clang-format
+CommentPragmas: '^stm:.*'