add "open in external editor" button to embedded editor

[avilleret]

when clicking the button, Qt should :

1. create a temporary file with the content of the embedded editor
2. open external editor defined in the Score's preference panel with this temp file
3. watch file modification and update embedded editor accordingly (should this work in both way ?)

file watching example https://github.com/OSSIA/score/blob/master/base/plugins/score-plugin-js/JS/JSProcessModel.cpp#L78

[jcelerier]

• [ ] External editor for audio
• [ ] External editor for MIDI
• [ ] External editor for scripts

What else ?

[bltzr]

I would like so much to have something like this for editing mapper devices !