Use single PIO manifest

Fixes: https://github.com/me-no-dev/ESPAsyncWebServer/issues/223

espressif32_library.json

@@ -1,23 +0,0 @@
-{
-  "name":"AsyncWebServer",
-  "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"
-  },
-  "version": "1.1.0",
-  "license": "LGPL-3.0",
-  "frameworks": "arduino",
-  "platforms":"espressif32",
-  "dependencies":
-  {
-    "name": "AsyncTCP"
-  }
-}

library.json

@@ -15,9 +15,15 @@
   "version": "1.1.0",
   "license": "LGPL-3.0",
   "frameworks": "arduino",
-  "platforms":"espressif",
-  "dependencies":
-  {
-    "name": "ESPAsyncTCP"
-  }
+  "platforms":"espressif8266, espressif32",
+  "dependencies": [
+    {
+      "name": "ESPAsyncTCP",
+      "platforms": "espressif8266"
+    },
+    {
+      "name": "AsyncTCP",
+      "platforms": "espressif32"
+    }    
+  ]
 }