[FEATURE] Add script for generating the class diagram

Author: oliverklee

.github/dependabot.yml

@@ -21,6 +21,7 @@ updates:
         - dependency-name: "phpunit/phpunit"
           versions: [ ">= 9.0.0" ]
         - dependency-name: "rector/rector"
+        - dependency-name: "tasuku43/mermaid-class-diagram"
       versioning-strategy: "increase"
       commit-message:
           prefix: "[Dependabot] "

composer.json

@@ -35,7 +35,8 @@
         "phpunit/phpunit": "8.5.42",
         "rawr/phpunit-data-provider": "3.3.1",
         "rector/rector": "1.2.10 || 2.0.7",
-        "rector/type-perfect": "1.0.0 || 2.0.2"
+        "rector/type-perfect": "1.0.0 || 2.0.2",
+        "tasuku43/mermaid-class-diagram": "0.1.3 || 0.2.1 || 0.3.0 || 0.4.1 || 0.5.0"
     },
     "suggest": {
         "ext-mbstring": "for parsing UTF-8 CSS"