Add typing stubs for Rollbar SDK

[johnwhelchel]

This would be great to have so one could use Rollbar with the various static type checkers, like mypy.

Thanks for considering!

[danielmorell]

I am definitely in favor of static typing! I can't make any promises or timelines just yet, but I will see what we can do.

[CharlieBenson-OH]

@danielmorell is this something you are actively working on now? I see that there is a branch with some work in it? master...added/typehints

[danielmorell]

@CharlieBenson-OH Yes that is currently a WIP. I have a bit more work to get types on the most commonly used functions. A lot of it is just getting MyPy to run successfully, even if we are still missing a lot of types.