Forward "UnoCommandResult" to wopi host

[GaZaTu]

Is your feature request related to a problem?

Initially I just wanted CallPythonScript to be fixed (which has been broken for some time now), but then I realized that it would actually be rather nice to get a response for all .uno:* commands so that i know a command that i triggered is actually complete without the wopi host having to guess.

Describe the solution you'd like

I would like Collabora to introduce a new postMessage call (from client to host) which just forwards all instances of unocommandresult back to the wopi host.

Additional context

In my testing I simply added

this._map.fire('postMessage', {msgId: 'UnoCommandResult', args: {commandName: commandName, success: success, result: obj.result}});

below

online/browser/src/layer/tile/CanvasTileLayer.js

Line 3180 in 1a287fd

this._map.fire('commandresult', {commandName: commandName, success: success, result: obj.result});

to get the communication to work