Added RAK11200 board variant support (#1177)

* Added RAK11200 board variant support

boards/wiscore_rak11200.json

@@ -0,0 +1,39 @@
+{
+  "build": {
+    "arduino":{
+      "ldscript": "esp32_out.ld"
+    },
+    "core": "esp32",
+    "extra_flags": "-DARDUINO_ESP32_DEV",
+    "f_cpu": "240000000L",
+    "f_flash": "40000000L",
+    "flash_mode": "dio",
+    "mcu": "esp32",
+    "variant": "WisCore_RAK11200_Board"
+  },
+  "connectivity": [
+    "wifi",
+    "bluetooth",
+    "ethernet",
+    "can"
+  ],
+  "frameworks": [
+    "arduino",
+    "espidf"
+  ],
+  "name": "WisCore RAK11200 Board",
+  "upload": {
+    "flash_size": "4MB",
+    "maximum_ram_size": 327680,
+    "maximum_size": 4194304,
+    "protocols": [
+      "esptool",
+      "espota",
+      "ftdi"
+    ],
+    "require_upload_port": true,
+    "speed": 460800
+  },
+  "url": "https://www.rakwireless.com",
+  "vendor": "RAKwireless"
+}