feat(module:mention): add mention component

[hsuanxyz]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[X] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[X] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[] Yes
[ ] No

Other information

[codecov]

Codecov Report

Merging #1182 into master will increase coverage by 0.05%.
The diff coverage is 99.53%.

@@            Coverage Diff             @@
##           master    #1182      +/-   ##
==========================================
+ Coverage   97.18%   97.23%   +0.05%     
==========================================
  Files         185      191       +6     
  Lines        7705     7926     +221     
  Branches     1015     1040      +25     
==========================================
+ Hits         7488     7707     +219     
- Misses         25       26       +1     
- Partials      192      193       +1

Impacted Files	Coverage Δ
components/mention/mention-suggestions.ts	100% <100%> (ø)
components/mention/mention-trigger.ts	100% <100%> (ø)
components/mention/mention.module.ts	100% <100%> (ø)
components/mention/mention.component.ts	99.39% <99.39%> (ø)
components/table/nz-table.component.ts	94.83% <0%> (-0.65%)	⬇️
components/input/index.ts	100% <0%> (ø)
components/input/public-api.ts	100% <0%> (ø)
... and 1 more

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[hsuanxyz]

@vthinkxie work done