Update plugin doc (#213)

Author: alessio-perugini

docs/plugins.md

@@ -16,7 +16,20 @@ The new information is hosted in the
 [plugin_firmware_index.json](https://downloads.arduino.cc/arduino-fwuploader/boards/plugin_firmware_index.json), which
 is generated by `generator.py`.
 
-## uno-r4-wifi-plugin
+## Portenta C33
+
+The source code can be found [here](https://github.com/arduino/portenta-c33-fwuploader-plugin).
+
+## Nina family
+
+The source code can be found [here](https://github.com/arduino/nina-fwuploader-plugin). Supported boards:
+
+- [MKR WiFi 1010](https://docs.arduino.cc/hardware/mkr-wifi-1010)
+- [Nano 33 IoT](https://docs.arduino.cc/hardware/nano-33-iot)
+- [UNO WiFi Rev2](https://docs.arduino.cc/hardware/uno-wifi-rev2)
+- [Nano RP2040 Connect](https://docs.arduino.cc/hardware/nano-rp2040-connect)
+
+## UNO R4 WiFi
 
 The source code can be found [here](https://github.com/arduino/uno-r4-wifi-fwuploader-plugin).