feat(comp: watermark): add watermark component (#924)

[tuchg]

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• The commit message follows our guidelines
• Tests for the changes have been added/updated or not needed
• Docs and demo have been added/updated or not needed

What is the current behavior?

What is the new behavior?

#924

Other information

[idux-bot]

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[codecov]

Codecov Report

Merging #930 (c1763af) into main (2955e7f) will decrease coverage by 0.39%.
The diff coverage is 84.22%.

@@            Coverage Diff             @@
##             main     #930      +/-   ##
==========================================
- Coverage   93.38%   92.98%   -0.40%     
==========================================
  Files         679      727      +48     
  Lines       66670    68392    +1722     
  Branches     5888     5892       +4     
==========================================
+ Hits        62261    63597    +1336     
- Misses       4409     4795     +386     

Impacted Files	Coverage Δ
...ponents/watermark/src/composables/useCalcBase64.ts	58.13% <58.13%> (ø)
packages/components/watermark/src/utils/index.ts	74.07% <74.07%> (ø)
packages/components/index.ts	96.38% <100.00%> (ø)
...s/components/watermark/__tests__/watermark.spec.ts	100.00% <100.00%> (ø)
packages/components/watermark/index.ts	100.00% <100.00%> (ø)
packages/components/watermark/src/Watermark.tsx	100.00% <100.00%> (ø)
packages/components/watermark/src/types.ts	100.00% <100.00%> (ø)
packages/components/alert/src/Alert.tsx	98.05% <0.00%> (-1.95%)	⬇️
packages/components/alert/__tests__/alert.spec.ts	100.00% <0.00%> (ø)
...ackages/components/button/__tests__/button.spec.ts	100.00% <0.00%> (ø)
... and 53 more

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[danranVm]

尽可能避免直接给参数进行赋值操作。
另外建议这里抽象成一个数据表, 会让你的代码灵活很多，后续也可以考虑让用户自定义这个数据表，做到可配置。

const densityMap = {
low: {width:1, height:1, ...},
mid:{...},
heght:{...}
}

[tuchg]

其实是有对应参数开放的，只需要调节参数就行，数据表做不到数据的动态调整吧

[danranVm]

在 PR 里关联一下对应的 issue 就好，没必要在把 API 设计贴过来了。