build(deps): bump base64 from 0.21.4 to 0.22.0

[dependabot]

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Bumps base64 from 0.21.4 to 0.22.0.

Changelog

Sourced from base64's changelog.

0.22.0

• DecodeSliceError::OutputSliceTooSmall is now conservative rather than precise. That is, the error will only occur if the decoded output cannot fit, meaning that Engine::decode_slice can now be used with exactly-sized output slices. As part of this, Engine::internal_decode now returns DecodeSliceError instead of DecodeError, but that is not expected to affect any external callers.
• DecodeError::InvalidLength now refers specifically to the number of valid symbols being invalid (i.e. len % 4 == 1), rather than just the number of input bytes. This avoids confusing scenarios when based on interpretation you could make a case for either InvalidLength or InvalidByte being appropriate.
• Decoding is somewhat faster (5-10%)

0.21.7

• Support getting an alphabet's contents as a str via Alphabet::as_str()

0.21.6

• Improved introductory documentation and example

0.21.5

• Add Debug and Clone impls for the general purpose Engine

Commits

• 5d70ba7 Merge pull request #269 from marshallpierce/mp/decode-precisely
• efb6c00 Release notes
• 2b91084 Add some tests to boost coverage
• 9e9c7ab Engine::internal_decode now returns DecodeSliceError
• a8a60f4 Decode main loop improvements
• a25be06 Simplify leftover output writes
• 9979cc3 Keep morsels as separate bytes
• 37670c5 Bump dev toolchain version (#268)
• 9652c78 v0.21.7
• 08deccf provide as_str() method to return the alphabet characters (#264)
• Additional commits viewable in compare view

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