chore(main): release 6.4.0

[release-please[bot]]

:robot: I have created a release beep boop

6.4.0 (2023-02-08)

Features

• add support for W3C ES256K (#462) (213924f)
• improve caching by only decoding jwks when necessary (#486) (78d3ed1)

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[release-please[bot]]

:robot: Release is at https://github.com/firebase/php-jwt/releases/tag/v6.4.0 :sunflower: