Add CODEOWNERS file

[pmaytak]

Changes proposed in this request

• Adds CODEOWNERS file.
• Remove redundant autoassign reviewer action.

About code owners

Code owners are automatically requested for review when someone opens a pull request that modifies code that they own.
When someone with admin or owner permissions has enabled required reviews, they also can optionally require approval from a code owner before the author can merge a pull request in the repository.