Bump version, update assets and upgrade PayButton client to v5.4.0 (#120

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Co-authored-by: xecdev <ecashinformer@gmail.com>

Update README for v5.1.0 (#113)

Co-authored-by: xecdev <ecashinformer@gmail.com>

Update README and bump version (#106)

* Update README and bump version

* Mention WordPress 6.9 compatibility

* Remove zip file

* Update stable tag

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Co-authored-by: xecdev <ecashinformer@gmail.com>

Merge pull request #79 from PayButton/update-readme-for-4.0.0

update readme

Merge pull request #74 from PayButton/update-readme-for-v3.3.0

Update Readme for v3.3.0

Readme nit.

Version bump.

Fixed changelog date.

Version bump

Added PayButton client version to readme