Fix flash size for WEMOS D1 mini

Author: ivankravets

boards/d1_mini.json

@@ -12,11 +12,11 @@
   "frameworks": [
     "arduino",
     "esp8266-rtos-sdk"
-  ], 
+  ],
   "name": "WEMOS D1 mini",
   "upload": {
     "maximum_ram_size": 81920,
-    "maximum_size": 1044464,
+    "maximum_size": 4194304,
     "require_upload_port": true,
     "resetmethod": "nodemcu",
     "speed": 115200