Deprecate on signature_pad 3.0.0

[lathonez]

@szimek is re-writing signature_pad in typescript. When that's done I think we should be able to deprecate this package.

• [ ] - update demo app to use singuare_pad^3.0.0
• [ ] - update readme / deprecation notice on NPM

[lathonez]

3.0.0.beta-2 was released a month back. Not going to mess with this until it's been published on npm as a final version

[Triplecorpse]

Any news?