[ImgBot] Optimize images

*Total -- 9,359.48kb -> 6,951.50kb (25.73%)

/images/news-feed-init.png -- 275.58kb -> 189.96kb (31.07%)
/images/news-feed-final.png -- 661.11kb -> 459.25kb (30.53%)
/images/notification-system-final.png -- 444.13kb -> 311.07kb (29.96%)
/images/chat-init.png -- 487.57kb -> 347.43kb (28.74%)
/images/notification-system-init.png -- 683.37kb -> 488.15kb (28.57%)
/images/kv-availability-and-consistency.png -- 613.10kb -> 446.22kb (27.22%)
/images/twitter-snowflake.png -- 388.45kb -> 283.77kb (26.95%)
/images/chat-final.png -- 733.32kb -> 539.51kb (26.43%)
/images/crawler-full.png -- 797.38kb -> 590.61kb (25.93%)
/images/url-shortener-init.png -- 148.72kb -> 111.28kb (25.18%)
/images/doe-kv-store.png -- 1,142.68kb -> 857.99kb (24.91%)
/images/crawler-init.png -- 244.27kb -> 183.76kb (24.77%)
/images/url-shortener-final.png -- 633.10kb -> 479.29kb (24.29%)
/images/rate-limiter.png -- 427.04kb -> 324.15kb (24.09%)
/images/hash-ring.png -- 290.29kb -> 222.91kb (23.21%)
/images/consistent-hashing.png -- 237.83kb -> 188.57kb (20.71%)
/images/zero-to-million.png -- 1,151.54kb -> 927.60kb (19.45%)

Signed-off-by: ImgBotApp <ImgBotHelp@gmail.com>

Author: ImgBotApp