docs: add some missing documents

[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

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What is the new behavior?

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[idux-bot]

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[codecov]

Codecov Report

Merging #1078 (35b8ed3) into main (e07eb87) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 35b8ed3 differs from pull request most recent head c1da418. Consider uploading reports for the commit c1da418 to get more accurate results

@@           Coverage Diff           @@
##             main    #1078   +/-   ##
=======================================
  Coverage   96.74%   96.74%           
=======================================
  Files         314      314           
  Lines       30256    30291   +35     
  Branches     2806     2812    +6     
=======================================
+ Hits        29271    29306   +35     
  Misses        985      985           

Impacted Files	Coverage Δ
packages/cdk/forms/src/utils.ts	75.52% <100.00%> (+2.85%)	⬆️

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