docs: Optimize images (#6)

*Total -- 996.20kb -> 663.02kb (33.45%)

/tests/test_data/samples/PHM.2013.page_30.png -- 170.02kb -> 59.12kb (65.23%)
/docs/tbm04.png -- 200.40kb -> 139.06kb (30.61%)
/docs/tablemodel_overview_color.png -- 237.23kb -> 171.40kb (27.75%)
/tests/test_data/samples/ADS.2007.page_123.png -- 388.55kb -> 293.44kb (24.48%)

Signed-off-by: ImgBotApp <[email protected]>
Co-authored-by: ImgBotApp <[email protected]>

Author: imgbot[bot]