Bump pymdown-extensions from 10.19.1 to v10.21.2

[dghubble-renovate]

This PR contains the following updates:

Package	Update	Change
pymdown-extensions	minor	==10.19.1 → ==10.21.2

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Release Notes

facelessuser/pymdown-extensions (pymdown-extensions)

v10.21.2: 10.21. 2

Compare Source

10.21.2

• FIX: Highlight: Latest Pygments versions cannot handle a "filename" for code block titles of None.

v10.21

10.21

• NEW: Caption: Add support for specifying not only IDs but classes and arbitrary attributes. Initial work by
  @​joapuiib.
• FIX: MagicLink: Fix a matching pattern for Bitbucket repo.

v10.20

Compare Source

10.20

• NEW: Quotes: New blockquotes extension added that uses a more modern approach when compared to Python Markdown's
  default. Quotes specifically will not group consecutive blockquotes together in the same lazy fashion that the
  default Python Markdown does which follows a more modern trend to how parsers these days handle block quotes.

  In addition, Quotes also provides an optional feature to enable specifying callouts/alerts in the style used by
  GitHub and Obsidian.

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