feat(comp:watermark): add custom props for canvas

[tuchg]

PR Checklist

Please check if your PR fulfills the following requirements:

• 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?

暴露水印组件的canvas，方便用户进行保密的暗水印方案实施

Other information

[idux-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #1154 (7e4a41e) into main (787f3f1) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1154   +/-   ##
=======================================
  Coverage   96.95%   96.95%           
=======================================
  Files         321      321           
  Lines       30871    30878    +7     
  Branches     2066     2066           
=======================================
+ Hits        29931    29938    +7     
  Misses        940      940           

Impacted Files	Coverage Δ
packages/components/watermark/src/types.ts	100.00% <100.00%> (ø)

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