[ImgBot] Optimize images

*Total -- 1,302.80kb -> 775.60kb (40.47%)

/docs/data_diagram.png -- 57.88kb -> 15.16kb (73.8%)
/docs/identify_language.png -- 359.46kb -> 187.05kb (47.96%)
/docs/nested_query.png -- 371.04kb -> 199.40kb (46.26%)
/docs/conveyor_belt.png -- 95.29kb -> 63.46kb (33.4%)
/docs/sanitization.png -- 53.71kb -> 38.45kb (28.42%)
/docs/links.png -- 59.69kb -> 43.64kb (26.9%)
/docs/mutations.png -- 85.90kb -> 62.88kb (26.8%)
/docs/resolution.png -- 55.85kb -> 41.21kb (26.21%)
/docs/translation.png -- 32.92kb -> 24.31kb (26.13%)
/docs/data-centric.png -- 45.68kb -> 33.92kb (25.75%)
/docs/auth.png -- 85.39kb -> 66.12kb (22.57%)

Signed-off-by: Alan Cha <[email protected]>

Author: ImgBotApp