enforce wheel size limits, README formatting in CI

[jameslamb]

Description

Contributes to rapidsai/build-planning#110

Proposes adding 2 types of validation on wheels in CI, to ensure we continue to produce wheels that are suitable for PyPI.

• checks on wheel size (compressed),
  • to be sure they're under PyPI limits
  • and to prompt discussion on PRs that significantly increase wheel sizes
• checks on README formatting
  • to ensure they'll render properly as the PyPI project homepages
  • e.g. like how https://github.com/scikit-learn/scikit-learn/blob/main/README.rst becomes https://pypi.org/project/scikit-learn/

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[jameslamb]

CI is blocked in this repo, because docs builds are failing like this:

/__w/rmm/rmm/python/rmm/docs/docstring of rmm.pylibrmm.device_buffer.DeviceBuffer.prefetch:10: WARNING: py:attr reference target not found: cuda.bindings.runtime.cudaCpuDeviceId

(build link)

@harrism pushed a fix for that to #1724 (5330063), but I'm not sure how close that PR is to being merged.

Proposing the same fix here, in this ready-to-merge PR, to help unblock CI.

[bdice]

Approving docs fix to unblock CI.

[jameslamb]

/merge