Update file(s) from wp-cli/.github

Merge pull request #105 from wp-cli/regenerate-readme

Regenerate README file

Merge pull request #97 from petitphp/fix/failing-tests-wp66

Merge pull request #94 from wp-cli/regenerate-readme

Regenerate README file

Merge pull request #90 from wp-cli/update-wp-cli-tests-v4

Add `wp cache flush-group` for flushing a cache group (#85)

* Added group flushing.

Needs extra input for testing.

* Added failsafe for older WP versions.

Also phpcs formatting.

* Processed feedback.

* Added test for error on clear-group

* Renamed clear-group to flush-group

Fixed failing test and generated readme file.

* Set correct error message in the test.

* Make sure a test only runs at 6.1 or later.

Warn when `wp transient list` is used with external object cache (#82)

Merge pull request #74 from wp-cli/fix/make-transient-delete-test-mor…

…e-robust

Merge pull request #73 from wp-cli/fix/adapt-branch-alias

Merge pull request #72 from wojsmol/fix/php8.1-compat