pre-commit: add oxipng for lossless PNG compression

[jbampton]

Tested here locally with pre-commit run --all-files

First time the oxipng hook failed and optimized the PNGs.

The second time the hook passed.

With GitHub actions it just works with pass and fail.

https://github.com/oxipng/oxipng

"Lossless compression reduces file size without losing any information, allowing the original data to be perfectly reconstructed upon decompression. It works by identifying and eliminating statistical redundancy in the data, making it ideal for situations where data integrity is critical, such as with text, charts, or raw images. Popular examples include the PNG and ZIP formats."

https://en.wikipedia.org/wiki/Lossless_compression

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