add platformio support

library.json

@@ -0,0 +1,21 @@
+{
+  "name":"ESPAsyncWebServer",
+  "description":"Asynchronous HTTP and WebSocket Server Library for ESP8266 and ESP32",
+  "keywords":"http,async,websocket,webserver",
+  "authors":
+  {
+    "name": "Hristo Gochkov",
+    "maintainer": true
+  },
+  "repository":
+  {
+    "type": "git",
+    "url": "https://github.com/me-no-dev/ESPAsyncWebServer.git"
+  },
+  "frameworks": "espressif",
+  "platforms":"arduino",
+  "dependencies":
+  {
+    "name": "ESPAsyncTCP"
+  }
+}