[llvm] Add Scorecard Action (PR #69933)

[Tom Stellard via llvm-commits]

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+# This workflow uses actions that are not certified by GitHub. They are provided
+# by a third-party and are governed by separate terms of service, privacy
+# policy, and support documentation.
+
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tstellar wrote:

Could add a comment with a link for where to view the results?

https://github.com/llvm/llvm-project/pull/69933