v1.1.1

[x] Create a release/v1.1.1 branch off of main for the release candidate.
Testing
- [x] Run functional_tests.yml workflow on release/v1.1.1.
[x] Create a GitHub release of release/v1.1.1 with a v1.1.1 tag.
- [x] Copy the release notes from the ## Unreleased section of CHANGELOG.md.
- [x] After the release is created, verify a git tag named v1.1.1 is pointing to the release/v1.1.1 branch
Git tag manipulation.
- [x] Move the v1 tag to point to release/v1.1.1.
[x] Verify action with uses: leanprover/lean-action@v1.1.1 in test repo as a sanity check.
Create a PR to:
- [x] Create a PR to update CHANGELOG.md with the latest release.
[ ] Post release announcement in general/lean-action Zulip topic.

leanprover / lean-action