markdown-modern 2.1.0

This release needs no setup changes. It adds a Mermaid diagram viewer, local file links and reference links, and fixes nested lists.

Thanks to Hemant Kumar (@gnufied) for local file links and two fixes, and to Samuel Michael Vanie (@SamuelVanie) for the Mermaid work.

• Click a Mermaid diagram, or press C-c C-v d in its source, to open it in a viewer. You can zoom and pan there.
• Mermaid flowcharts, sequence, state, class and ER diagrams draw more correctly. A diagram with a feature the renderer cannot draw, such as a subgraph, shows its source instead of a partial diagram.
• Local links open files in Emacs, relative to the Markdown file. #L352 and #L352-L365 go to that line. M-, goes back.
• Reference links render: [text][label], [text][] and [label]. Definition lines are dimmed.
• Nested list items show their bullet, number or checkbox again. Since 2.0.0 only the first level had one.
• Fix bold italic text that disappeared, line breaks next to inline code, and wrapped list text that did not line up.
• Fix C-c ' opening an empty buffer, and a link click that showed the link's markup first.
• Check all 313 tests on Emacs 30.1 and 31.1.

Download the tarball below and install it with M-x package-install-file, or follow the README.

To return to the previous release, install the package from tag 2.0.0.