add playtwitch script

scripts/playtwitch

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+# play a twitch stream using streamlink
+
+__usage="
+USAGE:
+    $0 <stream_name> [quality]
+
+ARGS:
+    <stream_name>   Name of the stream to play
+    [quality]       quality to use [default: best]
+"
+
+if [ -z $1 ] || [ $# -gt 2 ] || [ $1 = "--help" ]; then
+    echo -e "$__usage"
+else
+    streamlink https://twitch.tv/$1 ${2:-best}
+fi