doc: update begining doc

[paranoidjk]

close #1375

First of all, thank you for your contribution! :-)

Please makes sure that these checkboxes are checked before submitting your PR, thank you!

• Make sure that you follow antd's code convention.
• Run npm run lint and fix those errors before submitting in order to keep consistent code style.
• Rebase before creating a PR to keep commit history clear.
• Add some descriptions and refer relative issues for you PR.

Extra checklist:

if isBugFix :

• Make sure that you add at least one unit test for the bug which you had fixed.

elif isNewFeature :

• Update API docs for the component.
• Update/Add demo to demonstrate new feature.
• Update TypeScript definition for the component.
• Add unit tests for the feature.

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This change is 

[mention-bot]

@paranoidjk, thanks for your PR! By analyzing the history of the files in this pull request, we identified @warmhug, @pingan1927 and @silentcloud to be potential reviewers.

[codecov]

Codecov Report

Merging #1503 into master will decrease coverage by 14.75%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master    #1503       +/-   ##
===========================================
- Coverage   79.81%   65.06%   -14.76%     
===========================================
  Files         109      229      +120     
  Lines         109     2290     +2181     
  Branches       95      701      +606     
===========================================
+ Hits           87     1490     +1403     
- Misses         22      799      +777     
- Partials        0        1        +1

Flag	Coverage Δ
#rn	79.81% <ø> (ø)	⬆️
#web	64.32% <ø> (?)

Impacted Files	Coverage Δ
components/tab-bar/index.web.tsx	89.13% <0%> (ø)
components/pagination/style/index.web.tsx	0% <0%> (ø)
components/grid/index.web.tsx	73.07% <0%> (ø)
components/radio/RadioItem.web.tsx	95.45% <0%> (ø)
components/tabs/index.web.tsx	92% <0%> (ø)
components/wing-blank/index.web.tsx	100% <0%> (ø)
components/icon/style/index.web.tsx	0% <0%> (ø)
components/popover/index.web.tsx	100% <0%> (ø)
components/tag/index.web.tsx	53.84% <0%> (ø)
components/notice-bar/index.web.tsx	97.05% <0%> (ø)
... and 110 more

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