Mention gRPC Monitor service in Serial Monitor FAQ

Author: per1234

docs/FAQ.md

@@ -26,6 +26,9 @@ something that we're trying to avoid.
 There are many excellent serial terminals to chose from. On Linux or macOS, you may already have [screen][screen]
 installed. On Windows, a good choice for command line usage is Plink, included with [PuTTY][putty].
 
+Arduino CLI does provide a gRPC interface which offers the capability for powerful integration with custom monitors. See
+the [Monitor service documentation][monitor service].
+
 ## Additional assistance
 
 If your question wasn't answered, feel free to ask on [Arduino CLI's forum board][1].
@@ -34,3 +37,4 @@ If your question wasn't answered, feel free to ask on [Arduino CLI's forum board
 [1]: https://forum.arduino.cc/index.php?board=145.0
 [screen]: https://www.gnu.org/software/screen/manual/screen.html
 [putty]: https://www.chiark.greenend.org.uk/~sgtatham/putty/
+[monitor service]: rpc/monitor.md