Refactor to a monorepo with components, demo and docs under the same branch

[b2nil]

This PR is intended to:

• refactor this repo into a monorepo

  • all taro-ui-vue3 components, style, utils and types are moved to the directory of packages
  • docs are moved to the directory of website
  • taro-ui-vue3 demo is moved to the directory of demo
  • refactored all test, build and bundle settings and scripts

• fixed a number of component issues

  • fix(float-layout): should stop propagation of touchmove event, #95 (38464a3)
  • fix(action-sheet): should stop propagation of touchmove event (05d3565)
  • fix(modal): should stop propagation of touchmove event (0c394ec, 2db17c4)
  • fix(calendar): isVertical not working in h5 (d0f3a4a)
  • fix(calendar): should stop propagation of touchmove event (7164d10)

• a number of fixes and refactor in docs

  • chore: update docs to alpha.20 (08ab231)
  • refactor(docs): a series of custom theme fixes and refactor (0a99782, 40d8f99, 5d6b529, 1755465, e76e46e)
  • fix(docs): use component in markdown (5c7e7b2)
  • fix(docs): use a bigger demo frame (620e3b9)
  • fix(docs): el.dataset not defined when navigate to home (ce29006)