Add a "phan parsing..." text in the status bar.

[9brada6]

Hi... my project takes about 10-15 seconds to be parsed by phan... It will be very nice if there was an indicator in status bar that will say when the phan is parsing(like PHP Sniffer: validating... ).

Thanks.

[TysonAndre]

https://github.com/phan/phan/wiki/Speeding-up-Phan-Analysis may be of help if you haven't seen it yet.

To do this, I'd probably need to:

• Add some custom event type to notify the language client that phan was still parsing (and didn't crash), and what percentage progress was made. Emit it every second or so.
• Find out what API to call in vs code to update the status bar