Folder structure change to fit into west workspace

The folders are restructured so that freestanding projects can fork zoysia repo within west workspace. The recommended project template is given below:

• .west/config

[manifest]
path = manifest-repo
file = west.yml

[zephyr]
base = zephyr

[build]
dir-fmt = build/{board}/{app}

• manifest-repo/west.yml

manifest:
  self:
    path: manifest-repo

  remotes:
    - name: upstream
      url-base: https://jihulab.com/qiaowen

  projects:
    - name: firmware
      remote: upstream
      revision: master
      import: true

• .gitignore