app playground: listening for load progress

[rubenfiszel]

Hi,

If you load https://typefox.github.io/monaco-languageclient/ghp_appPlayground.html, you should see that first it loads a white editor and then the theme is loaded and it becomes properly themed. That's content/color shift that I'd like to avoid for our users. It would likely be enough for us to wait for the themeService to be loaded and waiting for that to show a properly themed overlay/progress bar. I was wondering if there were any suggestions around getting:

• progress of items being loaded so we can bump the progress bar
• know when the themeService is sufficiently loaded that it would display the proper colors
• know when the full editor + workspace has been loaded in case we want to avoid all content shift.