Use phpstan/extension-installer for proper config (#116)

phpstan-drupal is not being loaded due to missing includes, neither are
deprecation checks. This is fixed with extension-installer. This also
adds explicit dependencies so they aren't inherited just through
upgrade_status

Author: mglaman

composer.json

@@ -25,6 +25,9 @@
     },
     "require-dev": {
         "acquia/coding-standards": "^0.8.0",
+        "mglaman/phpstan-drupal": "^1.1",
+        "phpstan/extension-installer": "^1.1",
+        "phpstan/phpstan": "^1.6",
         "phpstan/phpstan-deprecation-rules": "^1.0",
         "phpunit/phpunit": "^9.5",
         "squizlabs/php_codesniffer": "^3.6"
@@ -36,7 +39,8 @@
             "dealerdirect/phpcodesniffer-composer-installer": true,
             "drupal/core-composer-scaffold": true,
             "ergebnis/composer-normalize": true,
-            "oomphinc/composer-installers-extender": true
+            "oomphinc/composer-installers-extender": true,
+            "phpstan/extension-installer": true
         },
         "platform": {
             "php": "7.4"

composer.lock

@@ -4,4 +4,4 @@ parameters:
         - docroot/modules/custom
         - docroot/themes/custom
         - docroot/profiles/custom
-        - tests
+        - tests