Tweak dev guide / readme
Tweak dev guide / readme

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=220059244

superbderrick/ExoPlayer,stari4ek/ExoPlayer,stari4ek/ExoPlayer,saki4510t/ExoPlayer,superbderrick/ExoPlayer,google/ExoPlayer,amzn/exoplayer-amazon-port,google/ExoPlayer,amzn/exoplayer-amazon-port,ened/ExoPlayer,ened/ExoPlayer,androidx/media,google/ExoPlayer,saki4510t/ExoPlayer,ened/ExoPlayer,amzn/exoplayer-amazon-port,superbderrick/ExoPlayer,stari4ek/ExoPlayer,androidx/media,saki4510t/ExoPlayer,androidx/media