Losslessly optimise png

[petecooper]

Savings of ~50% bytes-wise.

Latest ImageOptim used with lossless settings.

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[alan-maguire]

thanks for this! Process requires the OCA is signed before I can merge however.

[petecooper]

OCA signed shortly after PR submission and was stated as pending approval (or words to that effect).

[alan-maguire]

great, thank you! once that gets approved I will merge (should be soon hopefully)