[clang-tidy] Add .clang-tidy to configure HeaderFilterRegex

Add HeaderFilterRegex to ignore clang-tidy errors being thrown from the
files being included from the google3/ directory

Google-Bug-Id: 380138741
Change-Id: Iabcd2fcd7f63b3a20784ae0433e0e9437237f83b
Signed-off-by: David Tang <davtang@google.com>
1 file changed