Add online help field to rpc platform

Author: MatteoPologruto

Diff for: rpc/cc/arduino/cli/commands/v1/common.pb.go

@@ -99,6 +99,9 @@ message Platform {
   bool deprecated = 10;
   // Type of the platform.
   repeated string type = 11;
+  // A URL provided by the author of the platform's package, intended to point
+  // to their online help service.
+  Online help = 12;
 }
 
 message InstalledPlatformReference {
@@ -126,3 +129,9 @@ message Profile {
   // FQBN specified in the profile.
   string fqbn = 2;
 }
+
+message Online {
+  // A URL provided by the author of the platform's package, intended to point
+  // to their online help service.
+  string online = 1;
+}