phpstan support (#250)

* phpstan v1 + workflow

* Fix intend

* More fixes

* Update phpstan.neon

* phpstan level 2

* Move errors ignoring into phpstan.neon

* phpstan level 3

* Don't ignore templates folder

* Something from level 4

* Update phpstan.neon

composer.json

@@ -19,7 +19,8 @@
     },
     "require-dev": {
         "filp/whoops": "^2.15",
-        "maximebf/debugbar": "dev-master"
+        "maximebf/debugbar": "dev-master",
+        "phpstan/phpstan": "^1.10"
     },
     "autoload": {
         "psr-4": {