Add labeler action

[aaronc]

Add GitHub labeler action

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• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[clevinson]

Nice one :)

Some ideas for additional types of labelers / paths we could add:

• "proto" (propto/*)
• "tests" (tests/*, testutil/*)
• "cosmovisor" (cosmovisor/*)
• "rosetta" (contrib/rosetta/*)
• "keys" (client/keys/*)

[tac0turtle]

Love this!! More bots the better 😜