Allow supporting merge PRs with changelogger. (#27881)

* [not verified] Allow supporting merge PRs with changelogger.

* [not verified] Add changelog.

* [not verified] Update version number for CLI.

* [not verified] Upgrade changelogger reference in all plugins.

* [not verified] Add changelogs.

* [not verified] Also add support for default merge message from GH.

* [not verified] Add unit test for supporting merge in changelogger.

* [not verified] Remove unneeded capturing groups and added anchoring.

* [not verified] Apply coding standards.

* [not verified] Remove redundant test.

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/3751481256

composer.json

@@ -8,7 +8,7 @@
 	},
 	"require-dev": {
 		"yoast/phpunit-polyfills": "1.0.4",
-		"automattic/jetpack-changelogger": "^3.2.3"
+		"automattic/jetpack-changelogger": "^3.3.0-alpha"
 	},
 	"autoload": {
 		"classmap": [