chore: add firmware provider to providers docs

[cgilly2fast]

What does this PR do?

adds firmware provider auth information to the provider docs

How did you verify your code works?

Simple mdx change, provider working good in opencode for about a week

[github-actions[bot]]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions[bot]]

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No duplicate PRs found