Add support info for composer

composer.json

@@ -17,6 +17,10 @@
             "homepage": "http://seld.be"
         }
     ],
+    "support": {
+        "irc": "irc://irc.freenode.org/composer",
+        "issues": "https://github.com/composer/composer/issues"
+    },
     "require": {
         "php": ">=5.3.2",
         "justinrainbow/json-schema": "1.1.*",