doc: add closing string quote mark
doc: add closing string quote mark

nnarhinen/flowplayer-thumbnails,flowplayer/flowplayer-thumbnails,nnarhinen/flowplayer-thumbnails,blacktrash/flowplayer-thumbnails,rlugojr/flowplayer-thumbnails,blacktrash/flowplayer-thumbnails,rlugojr/flowplayer-thumbnails,flowplayer/flowplayer-thumbnails