Support anchor links in HTML model

[philippjfr]

Searches rendered HTML contents for anchor links and then does two things:

• If document is still initializing will scroll the anchor linked in the URL into view
• Attach click event listeners on all anchor links to ensure that they work across the shadow DOM

Fixes #6156

[codecov]

Codecov Report

Attention: Patch coverage is 69.23077% with 8 lines in your changes missing coverage. Please review.

Project coverage is 82.22%. Comparing base (d5e2155) to head (568e865).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
panel/tests/ui/pane/test_markup.py	69.23%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7258      +/-   ##
==========================================
- Coverage   82.24%   82.22%   -0.02%     
==========================================
  Files         337      337              
  Lines       50293    50348      +55     
==========================================
+ Hits        41362    41398      +36     
- Misses       8931     8950      +19     

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[hoxbro]

One small comment

[MarcSkovMadsen]

Will this also work when updating page dynamically?

[philippjfr]

Will this also work when updating page dynamically?

Yes