Add layer hit detection and event handling

[dnass]

No description provided.

[LeoDog896]

I do like the idea of using a second canvas to detect collisions and it should cover most cases. I'm sure a few edge cases will pop up as issues (for both the color detection && the Proxy handler, but I can't think of any as of now.

I'm unfamiliar with using Proxy so I'm not able to do too thorough of a review there.

If I were to avoid the Proxy usage, I would make a new object that spreads the functions of the current canvas and overrides any that I personally need, while keeping the same signature as the 2dContext, though that itself is also probably a lot of work (and maybe justification for a second PR)

Also, you should add the examples to the list in the main page.

[LeoDog896]

By the way, in regards to your Proxy type issue, it seems that Proxy just doesn't have the capabilities for this yet in TS.

Also, probably best to update the README with extra info for the API as well.

[dnass]

@LeoDog896 Thanks for your notes — made some changes to the touch handler. Other than the lack of proper TS support, the approach I'm using here feels to me like a good use case for Proxies so I'm going to stick with it for now unless I discover any major roadblocks. From the POV of library users I don't think it'll make much different. Will update the example page and readme to document the new features.