Release 1.1 tracking: Verification, changelog entries

[benjaoming]

For a list of open issues, see the 1.1 milestone: https://github.com/readthedocs/sphinx_rtd_theme/issues?q=is%3Aopen+is%3Aissue+milestone%3A1.1

This is a meta-level issue to track that new PRs for 1.1 have a little extra verification since CI tests have had difficulties

• [ ] https://github.com/readthedocs/sphinx_rtd_theme/pull/967 and https://github.com/readthedocs/sphinx_rtd_theme/pull/1330 - check with html4 writer
• [ ] https://github.com/readthedocs/sphinx_rtd_theme/pull/1116 - how old versions of pip accept setup.cfg?
• [ ] https://github.com/readthedocs/sphinx_rtd_theme/pull/1080 - changelog entry missing
• [ ] https://github.com/readthedocs/sphinx_rtd_theme/issues/1309 - anything necessary for upper bounds?
• [ ] https://github.com/readthedocs/sphinx_rtd_theme/pull/1215 - changelog entry missing
• [ ] https://github.com/readthedocs/sphinx_rtd_theme/pull/1334 - changelog entry missing
• [ ] https://github.com/readthedocs/sphinx_rtd_theme/pull/1084 - changelog entry missing

Updates incoming for every PR that needs verification + changelog entry.