Update Rust crate mdbook to ^0.4.22

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
mdbook	dependencies	patch	^0.4.21 -> ^0.4.22

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Release Notes

rust-lang/mdBook

v0.4.22

Compare Source

40c06f5...4844f72

Added

• Added a --chapter option to mdbook test to specify a specific chapter to test.
  #​1741
• Added CSS styling for <kbd> tags.
  #​1906
• Added pre-compiled binaries for x86_64-unknown-linux-musl and aarch64-unknown-linux-musl (see Releases).
  #​1862
• Added build.extra-watch-dirs which is an array of additional directories to watch for changes when running mdbook serve.
  #​1884

Changed

• Removed the type="text/javascript" attribute from <script> tags.
  #​1881
• Switched to building with Rust Edition 2021.
  This raises the minimum supported Rust version to 1.56.
  #​1887
• When hidden code is hidden, the hidden parts are no longer copied to the clipboard via the copy button.
  #​1911
• Various HTML changes and fixes to be more compliant with HTML5.
  #​1924
• The theme picker now shows which theme is currently selected.
  #​1935

Fixed

• Avoid blank line at the end of an ACE code block
  #​1836

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