feat(module: tree): sync ant style & add dir demo

[simplejason]

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
[x] 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
[ x ] No

Other information

[vthinkxie]

https://deploy-preview-1559--ng-zorro-master.netlify.com/components/tree/zh
loading的样式飞了

[codecov]

Codecov Report

Merging #1559 into master will increase coverage by 0.11%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1559      +/-   ##
==========================================
+ Coverage   96.92%   97.03%   +0.11%     
==========================================
  Files         222      224       +2     
  Lines        9514     9766     +252     
  Branches     1299     1340      +41     
==========================================
+ Hits         9221     9476     +255     
+ Misses         43       42       -1     
+ Partials      250      248       -2

Impacted Files	Coverage Δ
components/tree/nz-tree-node.component.ts	94.38% <100%> (+0.19%)	⬆️
components/upload/nz-upload-list.component.ts	100% <0%> (ø)	⬆️
components/upload/nz-upload-btn.component.ts	100% <0%> (ø)	⬆️
components/upload/nz-upload.component.ts	100% <0%> (ø)	⬆️
components/transfer/nz-transfer.component.ts	100% <0%> (ø)	⬆️
components/tree/nz-tree.component.ts	100% <0%> (ø)	⬆️
components/tree-select/nz-tree-select.module.ts	100% <0%> (ø)
components/tree-select/nz-tree-select.component.ts	98.54% <0%> (ø)
components/pagination/nz-pagination.component.ts	99.27% <0%> (+0.03%)	⬆️
... and 5 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8a6b03d...9da29c0. Read the comment docs.