Include transition guide for using mouse/touch events from 1.x to 2.x

[ksen0]

From the 3 compatibility addons, data.js is the one that reinstantes 1.x usage.

This issue is opened to add a short summary / transition guide to the README: if a person uses events in their 1.x sketch, what do they need to change and how? Preferably, this would be side by side code like other sections.

Related issues:

• [p5.js 2.0 Beta Bug Report]: mouseButton returns false p5.js#7753

Delated documentation:

• the 1.x mouseButton --> the 2.x mouseButton

[mudit06mah]

I would like to take this issue!