Pymdown-extensions

- **NEW**: Blocks: Blocks extensions no longer considered in beta.
- **NEW**: Details: Details is marked as "legacy" in documentation in favor of the new `pymdownx.blocks.details` approach.
- **NEW**: Tabbed: Tabbed is marked as "legacy" in documentation in favor of the new `pymdownx.blocks.tab` approach.
- **NEW**: Caption: Add new "blocks" style extension called Caption which helps with specifying figures with captions.
- **NEW**: Emoji: Add a new `strict` option that will raise an exception if an emoji is used whose name has changed,
removed, or never existed.
- **FIX**: Emoji: Emoji links should be generated such that they point to the new CDN version.

- **FIX**: SuperFences: Fix a regression where certain patterns could cause a hang.

- **Fix**: SuperFences: Fix regression where an omitted language in conjunction with options in the fenced header
can cause a fence to not be parsed.

- **NEW**: SuperFences: Allow fenced code to be parsed in the form ` lang {.class id} `.

- **FIX**: BetterEm: Add better support for `*em, **em,strong***` and `_em, __em,strong___` cases.
- **FIX**: Caret: Add better support for `*sup, **sup,ins***`.
- **FIX**: Tilde: Add better support for `*sub, **sub,del***`.

- **FIX**: FancyLists: Remove a mistaken semicolon from injected classes.