docs/install: shell code blocks, remove prompts
docs/install: shell code blocks, remove prompts

melmorabity/streamlink,chhe/streamlink,streamlink/streamlink,chhe/streamlink,beardypig/streamlink,bastimeyer/streamlink,beardypig/streamlink,wlerin/streamlink,streamlink/streamlink,bastimeyer/streamlink,melmorabity/streamlink,gravyboat/streamlink,gravyboat/streamlink,wlerin/streamlink