Make demo pages meet lighthouse a11y best practices

[cdrini]

Pass failing lighthouse accessibility checks on the demo pages html. Also makes them more in sync with archive.org.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.48%. Comparing base (89fa996) to head (93195c8).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1455   +/-   ##
=======================================
  Coverage   69.48%   69.48%           
=======================================
  Files          62       62           
  Lines        5306     5306           
  Branches     1149     1149           
=======================================
  Hits         3687     3687           
  Misses       1585     1585           
  Partials       34       34           

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[Copilot]

Pull request overview

This PR improves the accessibility of BookReader demo pages to meet Lighthouse a11y best practices and align with archive.org standards. The changes address two key accessibility issues: missing language declarations and restrictions on user zoom capability.

Key changes:

• Added lang="en" attribute to all HTML pages for proper language declaration
• Removed maximum-scale=1.0, user-scalable=no from viewport meta tags to allow users to zoom pages
• Fixed malformed HTML in demo-preview-pages.html and wrapped checkboxes in labels in demo-internetarchive.html

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
index.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/viewmode-cycle.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/view_mode.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/toggle_controls.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/immersion-mode.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/immersion-1up.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/demo-vendor-fullscreen.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/demo-simple.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/demo-preview-pages.html	Added lang attribute, removed zoom restrictions, and fixed malformed viewport meta tag
BookReaderDemo/demo-multiple.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/demo-internetarchive.html	Added lang attribute, removed zoom restrictions, and wrapped checkboxes in labels for improved accessibility
BookReaderDemo/demo-iiif.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/demo-fullscreen.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/demo-fullscreen-mobile.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/demo-embed.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/demo-embed-iframe-src.html	Added lang attribute and removed zoom restrictions from viewport
BookReaderDemo/demo-advanced.html	Added lang attribute and removed zoom restrictions from viewport

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