add phpstan dependency, cut PHP 7.0 compatibility

composer.json

@@ -18,10 +18,15 @@
       }
     ],
     "require": {
-        "php": "^7.0 || ^8.0",
+        "php": "^7.1 || ^8.0",
         "oxid-esales/oxideshop-ce": "6.7 - 6.10",
         "d3/linkmobility-php-client": "^1.2.0 || ^2.0.0"
     },
+    "require-dev": {
+      "oxid-esales/oxideshop-ce": "~6.10.0",
+      "friendsofphp/php-cs-fixer": "^2.19",
+      "phpstan/phpstan": "^1.8"
+    },
     "extra": {
       "oxideshop": {
         "source-directory": "/src",

phpstan.neon

@@ -0,0 +1,7 @@
+parameters:
+    scanFiles:
+      - src/IntelliSenseHelper.php
+    paths:
+        - src
+    level: 0
+    phpVersion: 70100