Add support for DFRobot Firebeetle2 ESP32-C6 (#287)

This commit introduces initial support for the
DFRobot Firebeetle2 ESP32-C6 board, including its
configuration file.

Author: epsilonrt

boards/dfrobot_firebeetle2_esp32c6.json

@@ -0,0 +1,38 @@
+{
+  "build": {
+    "core": "esp32",
+    "extra_flags": [
+      "-DARDUINO_DFROBOT_FIREBEETLE_2_ESP32C6",
+      "-DARDUINO_USB_MODE=1",
+      "-DARDUINO_USB_CDC_ON_BOOT=1"
+    ],
+    "f_cpu": "160000000L",
+    "f_flash": "80000000L",
+    "flash_mode": "qio",
+    "mcu": "esp32c6",
+    "variant": "dfrobot_firebeetle2_esp32c6"
+  },
+  "connectivity": [
+    "wifi",
+    "bluetooth",
+    "zigbee",
+    "thread"
+  ],
+  "debug": {
+    "openocd_target": "esp32c6.cfg"
+  },
+  "frameworks": [
+    "arduino",
+    "espidf"
+  ],
+  "name": "DFRobot FireBeetle 2 ESP32-C6",
+  "upload": {
+    "flash_size": "4MB",
+    "maximum_ram_size": 327680,
+    "maximum_size": 4194304,
+    "require_upload_port": true,
+    "speed": 460800
+  },
+  "url": "https://wiki.dfrobot.com/SKU_DFR1075_FireBeetle_2_Board_ESP32_C6/",
+  "vendor": "DFRobot"
+}