Use shell script language for bats files (#24877)

bats is a superset of bash. It's a common tool for writing TAP tests in
bash.

https://bats-core.readthedocs.io/en/stable/tutorial.html#your-first-test

Release Notes:

- Added recognition for `.bats` files as "Shell Script".

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Co-authored-by: Marshall Bowers <git@maxdeviant.com>