chore: add extraPermissions to generate action.yml

[sekhar-isovalent]

add extraPermissions to add permissions-variables and permissions-attestations as generator based on openapi spec is broken

Fixes:

#310
#231

[sekhar-isovalent]

@gr2m - FYI. Appreciate if this can be integrated.

[parkerbxyz]

Thanks for the contribution! The missing permissions are a real pain point (as noted in #310 and #231).

I'd prefer to avoid hard-coding extraPermissions in the generator script though, since it could drift again as new permissions are added upstream.

The root cause is that the OpenAPI override files in octokit/openapi have fallen out of sync with the actual API. There's an open PR to start addressing that: octokit/openapi#529. Once the overrides are resynced upstream, the generator should pick up attestations, variables, organization-variables, and any other missing permissions automatically.

I'd prefer to fix this at the source rather than maintain a hardcoded list here, so I'm going to close this in favor of the upstream fix.