feat(module:mention): support standalone component

[ParsaArvanehPA]

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

What is the current behavior?

Updated Mention component to work as a standalone component.

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[✔] No

Other information

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5fd0b31) 91.70% compared to head (f6a5c20) 91.72%.
Report is 35 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8243      +/-   ##
==========================================
+ Coverage   91.70%   91.72%   +0.01%     
==========================================
  Files         519      518       -1     
  Lines       17887    17887              
  Branches     2836     2837       +1     
==========================================
+ Hits        16403    16406       +3     
+ Misses       1182     1180       -2     
+ Partials      302      301       -1     

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[Nicoss54]

Make the build pass again