6.0.0

Fixed

• MarkdownView now reads MarkdownRenderingOptions.renderMath. Until now only MathText
  read it, so passing renderMath: false still typeset the math in the document.
  Images and Mermaid render as before.
• MarkdownEditor no longer overwrites the theme's baseFontSize. The font size of the theme
  placed in the environment now takes effect as it is.

Removed

• Removed baseFontSize from the MarkdownEditor initializer. MarkdownEditorTheme is now
  the one place that decides the body text size.
• Removed RuleTransform.allowCoalescing. No rule set it and nothing read it.
• Removed the .markdownSource attribute key. It was written in 4 places and had no reader.

Changed

• Put the toolbar labels, the mode picker display names, and the logs for image, Mermaid, and highlighting failures into English.