chore: Add PHP8.0 polyfill due to str_starts_with function usage (#12)

Author: Greg0

composer.json

@@ -37,7 +37,8 @@
   "require": {
     "php": "^7.4 || ^8.0",
     "ext-json": "*",
-    "psr/log": "^1.1"
+    "psr/log": "^1.1",
+    "symfony/polyfill-php80": "^1.33"
   },
   "require-dev": {
     "phpunit/phpunit": "^9",