Merge pull request #6632 from opf/fix/28434/strikethrough

[28434] Ensure strikethrough is double-tile everywhere

[ci skip]

docs/user/text-formatting/README.md

@@ -2,7 +2,8 @@ Starting with version 8.0.0, OpenProject features a quasi-WYSIWYG editor, powere
 
 ## Basic formatting
 
-The CKEditor5 build in OpenProject supports basic text styles, such as bold and italic formatting, headings, inline code and quotes as well as inline image handling. Pasting content such as images or rich text is also supported, while unsupported styling will be stripped by the editor.
+The CKEditor5 build in OpenProject supports basic text styles, such as bold and italic formatting, headings,
+strikethrough, inline code, and quotes as well as inline image handling. Pasting content such as images or rich text is also supported, while unsupported styling will be stripped by the editor.
 
 ### Links
 

lib/open_project/text_formatting/filters/markdown_filter.rb

@@ -42,7 +42,7 @@ module OpenProject::TextFormatting
       # Get initial CommonMarker AST for further processing
       #
       def parse
-        parse_options = %i[LIBERAL_HTML_TAG]
+        parse_options = %i[LIBERAL_HTML_TAG STRIKETHROUGH_DOUBLE_TILDE]
 
         # We need liberal html tags thus parsing and rendering are several steps
         # Check: We may be able to reuse the ast instead of rendering to html and then parsing with nokogiri again.