Explicitly set php supported version to composer.json

Set the php version require help to get sync composer with IDE and other
dev tools.

Author: widoz

composer.json

@@ -27,13 +27,15 @@
   ],
   "minimum-stability": "stable",
   "require": {
+    "php": ">=7.0",
     "squizlabs/php_codesniffer": "^3.02",
     "dealerdirect/phpcodesniffer-composer-installer": "^0.4",
     "wp-coding-standards/wpcs": "^0.14",
     "automattic/phpcs-neutron-standard": "^1",
     "wimg/php-compatibility": "^8.0"
   },
   "require-dev": {
+    "php": ">=7.0",
     "phpunit/phpunit": "6.0.*"
   },
   "autoload-dev": {