Add bespoke template

[yhatt]

This PR will add "bespoke" template to supported templates. As the name suggests, this template is using bespoke.js.

It has super-simple and customizable ecosystem for HTML presentation, so it is the best solution for converted Marp slide deck.

• Add classes - Based on bespokejs/bespoke-classes, but we only support adding to active slide.
• Navigation - We are using bespokejs/bespoke-keys, and support additional keys and clever wheel navigation.
• Touch support - Implemented better swipe support for touch devices.
• URL hash support - Based on bespokejs/bespoke-hash, but we replace history, don't stack.
• Hide cursor when inactive - Add bespoke-marp-cursor-inactive class when cursor is idle.
• Progress bar - Bespoke template has a support of progress bar (disabled by default), and we will implement template option by configuration file in future.

It will become to be able HTML based presentation on browser. Try this HTML!! (an example of uncover theme) For actual presentation, you have to hit F11 key to get full-screen view.

It can close yhatt/marp#105, and it works as a workaround of presentation mode (yhatt/marp#13). However, we are planning much better presentation mode implementation in marp-team/marp-web repository (like presenter tools, multi-screen support using Presentation API).

ToDo

• Add tests in browser context

[yhatt]

Testing for bespoke template was filled! 🎉
We are ready to be able using converted HTML in actual presentation.

Example HTML (using uncover theme) is here.

We recommend using with the latest Firefox. Renderings on other browsers seem not to work correctly.

• Chrome (Almost good)
  • Wrong auto scaling on Mac
  • Wrong hitting area of link
• Edge (Almost good)
  • Ignores background image filter
• Safari (Bad)
  • Auto scaling is not working 😭