Use Peg$ prefix for types instead of I

[ghost]

Fwik the TypeScript community now sees the I prefix as an antipattern and is moving away from it.
microsoft/TypeScript-Handbook#121
I would suggest Peg$ prefix for some similarity to the original PEG.js JavaScript output!

[pjmolina]

I see your point about style conventions.
However change it now would make a breaking change for its current users.
I will postpone such change when doing a major refactor (grouped with other breaking changes).

[ghost]

Okay, thanks for clarifying.. best to not make a PR until a major refactor is done :)

[iccicci]

What about an option which defaults to "I"?
That would give a way to solve the problem without being a breaking change.

[pjmolina]

Removed prefix on v. 3.0.0 with breaking change. Decided to do it this way to keep it as simple as possible.