fix: calculate EXT-X-START TIME-OFFSET from actual playlist end for live streams#1599

Essk merged 1 commit intovideojs:mainvideojs/http-streaming:mainfrom

LorDisturbia:fix/ext-x-start-live-edge-delayLorDisturbia/http-streaming:fix/ext-x-start-live-edge-delayCopy head branch name to clipboard