Update docs to mention ignoreMinBufferTime
Update docs to mention ignoreMinBufferTime

Issue #1547 (introduced manifest.dash.ignoreMinBufferTime config)
Issue #1666 (in which ignoreMinBufferTime is discussed as a solution)

Change-Id: I895dc136ab7a4900ee74ff8ebe60b2bc194efe32

shaka-project/shaka-player,tvoli/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,tvoli/shaka-player