Add esp32c3

Author: fvanroie

platformio.ini

@@ -17,6 +17,7 @@ extra_configs =
     user_setups/esp32/_esp32.ini
     user_setups/esp32s2/_esp32s2.ini
     user_setups/esp32s3/_esp32s3.ini
+    user_setups/esp32s3/_esp32c3.ini
     ; --  Put custom [env] files in this dir to be included in the build menu
     user_setups/custom/*.ini
     ; --  Add customizations to this file only (copy and rename the template):