fix: support reading GH files above 1MB

[iblankJC]

Resolves #2836

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Before the change?

• Fails to read files larger than 1MB with error: unsupported content encoding: none

After the change?

• Checks GitHub content encoding and uses appropriate Accept header
• Supports reading repository files larger than 1MB

Pull request checklist

• Schema migrations have been created if needed (not needed)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

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[github-actions]

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