feat(module:page-header): add default behavior for the back button

[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
[ ] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #3421

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[netlify]

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Built with commit 024c82a

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[codecov]

Codecov Report

Merging #3891 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3891      +/-   ##
==========================================
+ Coverage   95.23%   95.24%   +<.01%     
==========================================
  Files         726      726              
  Lines       14672    14676       +4     
  Branches     1910     1911       +1     
==========================================
+ Hits        13973    13978       +5     
  Misses        260      260              
+ Partials      439      438       -1

Impacted Files	Coverage Δ
components/page-header/nz-page-header.component.ts	100% <100%> (ø)	⬆️
components/time-picker/time-holder.ts	97.26% <0%> (+0.68%)	⬆️

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[wzhudev]

lgtm