chore: support standalone of site

[cipchk]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ng-alain/delon/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

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[ ] No

Other information

[ng-alain-bot]

Preview is ready!

[codecov]

Codecov Report

Merging #1696 (02b4d18) into master (da051b2) will not change coverage.
The diff coverage is n/a.

❗ Current head 02b4d18 differs from pull request most recent head 450331c. Consider uploading reports for the commit 450331c to get more accurate results

@@           Coverage Diff           @@
##           master    #1696   +/-   ##
=======================================
  Coverage   95.45%   95.45%           
=======================================
  Files         300      300           
  Lines        8821     8821           
  Branches     1658     1658           
=======================================
  Hits         8420     8420           
  Misses        331      331           
  Partials       70       70