convert stub file function declarations into QScintilla autocompletion schema

[Jeffrey04]

refs: #2291

Usage:

python utils/completion_convert.py <stub_file dir> <output_filepath>

[Jeffrey04]

I suppose I should have used ast to parse the stub file

[Jeffrey04]

am aware of the code only work for one file for now, working on traversing the directory next
(is there a way to not trigger a build until this PR is ready?)

[Jeffrey04]

for https://github.com/oivron/microbit-stubs/blob/master/microbit/lib/audio.py

script current returns a file

MICROBIT_APIS = [_("play(source, wait, pins) Play the source to completion where 'source' is an iterable, each element of which must be an AudioFrame instance."), _("is_playing() Return True if audio is playing, otherwise return False."), _("stop() Stops all audio playback.")]

[Jeffrey04]

code should now generate the autocompletion guide, it is hackish, and most certainly require a lot of polishing, please let me know if I missed out anything that require fixing