feat: replace onFullScreenChange with onEvent

[ambar]

添加 onEvent 作为 MessageContext 通讯的替代方式，MessageContext 有两个缺陷：

• 它依赖 didmount/useEffect，如果触发的事件比较早就会监听不到
• 使用比较麻烦，需要注销监听，并且依赖额外的包（griffith-message），这个 PR 同时把 EVENTS 对象导出了

现在的替代使用方式是：

import Player, {EVENTS} from 'griffith'

render(
  <Player
    onEvent={type => {
      if (type === EVENTS.PLAYER.REQUEST_PLAY) {
        ...
      }
    }}
  />
)

新旧使用方式在 example/src/MP4Page.jsx 中都有体现。

[codecov-commenter]

Codecov Report

Merging #175 (c5caf55) into master (2d8d444) will increase coverage by 0.05%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #175      +/-   ##
==========================================
+ Coverage   48.67%   48.72%   +0.05%     
==========================================
  Files         128      128              
  Lines        1847     1845       -2     
==========================================
  Hits          899      899              
+ Misses        948      946       -2     

Impacted Files	Coverage Δ
packages/griffith/src/components/Player/Player.js	0.00% <0.00%> (ø)
.../src/components/PlayerContainer/PlayerContainer.js	0.00% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2d8d444...c5caf55. Read the comment docs.

[ambar]

应该 hook 化，把这里的所有 Consumer 都删掉（在各自组件内使用 useContext），props 就能直接传递下去不需要 sequence