[frontend-gray] Increase gray types according to the ratio-weight gray

[heimanba]

Ⅰ. Describe what this PR did

1. 增加按照比例灰度的能力,YAML配置如下： 灰度规则 beta-user的灰度范围为 50%

baseDeployment: 
  version: "dev"
grayDeployments: 
- name: "beta-user"
  version: "0.0.1"
  enabled: "true"
  weight: "50"

2. 添加往首页注入脚本的能力 可以分别在 header，body的首部first和尾部last注入相关代码。

---
injection: 
  header: 
  - "<script>console.log('Header')</script>"
  body: 
    first: 
    - "<script>console.log('hello world before')</script>"
    - "<script>console.log('hello world before1')</script>"
    last: 
    - "<script>console.log('hello world after')</script>"
    - "<script>console.log('hello world after2')</script>"

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews