refactor: VuePress to VitePress

[bavoco]

This reduces the number of dev dependencies by about 700.

Towards #812

[NotTsunami]

By nature, the move from VuePress -> VitePress should also allow us to drop the babel dependencies too, right? A very brief peek at the source suggests it is not used outside of VuePress.

[NotTsunami]

I tested it on your branch and npm run docs passes with the babel dependencies removed. With @babel/core, @babel/preset-env, and babel-loader removed, another 155 packages are removed. npm run test passes with 76/76 tests while npm run lint and npm run build complete without error.

[NotTsunami]

You should be able to remove ng-hammerjs as well, since it was only used in VuePress:

chartjs-plugin-zoom/docs/.vuepress/config.js

Lines 89 to 90 in bfd207d

	// Hammerjs requires window, using ng-hammerjs instead
	'hammerjs': 'ng-hammerjs',

[bavoco]

Great! If #808 gets merged there won't be two versions of Rollup and related plugins further reducing the count.