Refactor HTML to remove type attribute from style tags

[pardeyke]

This pull request standardizes the way CSS stylesheets and style elements are included throughout the project by removing the unnecessary type="text/css" attribute from <link> and <style> tags. This change simplifies the code and aligns with current HTML standards, as specifying the type is no longer required.

[Copilot]

Pull request overview

This PR aligns the project’s HTML/CSS inclusion patterns with modern HTML standards by removing the redundant type="text/css" attribute from <style> and stylesheet <link> tags across source, docs, test fixtures, and the Action Text bundled build.

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Changes:

• Removed type="text/css" from dynamically created <style> elements used for per-custom-element default CSS.
• Updated test fixtures and test helper HTML-injection to use bare <style> tags.
• Updated documentation and static HTML assets to omit type="text/css" on stylesheet links and style blocks.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/trix/core/helpers/custom_elements.js	Stops setting type="text/css" on injected <style> elements (keeps nonce + data attributes intact).
action_text-trix/app/assets/javascripts/trix.js	Mirrors the same removal in the bundled Action Text JS artifact.
src/test/test_helper.js	Updates global test <style> injection to omit the type attribute.
src/test/test_helpers/fixtures/editor_with_styled_content.js	Updates fixture <style> tag to omit the type attribute.
src/test/test_helpers/fixtures/editor_with_bold_styles.js	Updates fixture <style> tag to omit the type attribute.
src/test/test_helpers/fixtures/editor_with_block_styles.js	Updates fixture <style> tag to omit the type attribute.
README.md	Updates CDN usage example to omit type="text/css" on the stylesheet link.
assets/test.html	Updates stylesheet link to omit type="text/css".
assets/index.html	Updates stylesheet link and inline <style> to omit type="text/css".

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