fix(module:schematics): import RouterLink

[JavaProgrammerLB]

Every time 'side-menu' is chosen when adding ng-zorro-antd into Angular project, app.component.html uses RouterLink in Dashboard/welcome router, but the Routerlink is not imported in app.component.ts, I have to import RouterLink in app.component.html whenever I create a new project.

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?

Issue Number: N/A

1. Choose sidemenu when import ng-zorro-antd

2. the generated app.component.html used 'RouterLink' without 'RouterLink' in import code block

3. The 'RouterLink' is missed

What is the new behavior?

import RouterLink

Does this PR introduce a breaking change?

• Yes
• No

Other information

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.50%. Comparing base (589a842) to head (e156ddf).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8621      +/-   ##
==========================================
- Coverage   91.51%   91.50%   -0.02%     
==========================================
  Files         534      534              
  Lines       18425    18425              
  Branches     2905     2905              
==========================================
- Hits        16862    16860       -2     
- Misses       1243     1244       +1     
- Partials      320      321       +1     

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[HyperLife1119]

LGTM