General fixes

This release addressed issues affecting custom markup in Rich Text editors, previews of SVG files, and screenshots in the Sites browser.

Fixes#

• Fixed an issue where Sites with allow_custom_markup: false did not create uneditable snippets for links with non-standard attributes (e.g., id, data) in Rich Text editors.
• Fixed an issue where previews for SVG files did not work.
• Fixed an issue where screenshots on the Sites browser were broken.