* Change all icons to be white background
* assets: re-processed all *.png images to 1-bit
* assets: also stripped profile data from .pngs
* assets: also stripped datetime from metadata (`-define png:exclude-chunks=date,time`)
* scripts: added image linter and formatter; fbt: added `lint_img` && `format_img` targets; github: integrated image lint step into CI
* scripts: imglint: fixed deprecation warning
* images: applied `format_img`
* fbt: added `lint_all` and `format_all` targets; docs: updated for new targets
Co-authored-by: hedger <hedger@nanode.su>
Co-authored-by: hedger <hedger@users.noreply.github.com>
