up php version to 7.4 and add to ignore .idea

Author: Andrey Romashov

.gitignore

@@ -4,3 +4,4 @@
 TAG_MESSAGE
 /.phpunit.result.cache
 /.php_cs.cache
+/.idea/

composer.json

@@ -19,7 +19,7 @@
         ]
     },
     "require": {
-        "php": "^7.2",
+        "php": "^7.4",
         "ext-soap": "*",
         "symfony/options-resolver": "^3.4 || ^4.3 || ^5.0",
         "symfony/polyfill-iconv": "^1.13.1"