Add another psr-4 prefix, update composer packages

Previously it was just "gullevek\dotEnv" but now also "gullevek\dotenv"
will work.

Update phan/phpstan composer dev requirement verisons

composer.json

@@ -6,7 +6,8 @@
     "license": "MIT",
     "autoload": {
         "psr-4": {
-            "gullevek\\dotEnv\\": "src/"
+            "gullevek\\dotEnv\\": "src/",
+            "gullevek\\dotenv\\": "src/"
         }
     },
     "authors": [
@@ -26,7 +27,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^9",
-        "phpstan/phpstan": "1.10.x-dev",
-        "phan/phan": "v5.x-dev"
+        "phpstan/phpstan": "^1.10",
+        "phan/phan": "^5.4"
     }
 }