Clean up scripts

Signed-off-by: Severin Kaderli <severin@kaderli.dev>

system/.local/bin/twitch

@@ -1,26 +1,16 @@
-#!/usr/bin/env bash
-# 
-# SCRIPT NAME:
-# twitch
-#
-# AUTHOR:
-# Severin Kaderli <severin@kaderli.dev>
-#
-# DESCRIPTION:
-# This script loads a Twitch livestream in a local video player
-# using streamlink.
-#
-# USAGE:
-# ./twitch USERNAME [RESOLUTION]
-if [[ -z $1 ]]; then
-  echo "Please enter a username!"
+#!/usr/bin/env sh
+
+usage () {
+  echo "Usage: $(basename "${0}") <username> [<resolution>]"
+  echo "Plays a stream from twitch.tv in a local video player."
   exit 1
+}
+
+if [ -z "${1}" ]; then
+  usage
 fi
 
-if [[ -z $2 ]]; then
-  resolution="best"
-else
-  resolution="${2}"
-fi
+username="${1}"
+resolution="${2:-"best"}"
 
-streamlink "https://twitch.tv/${1}"  "${resolution}"
+streamlink "https://twitch.tv/${username}"  "${resolution}"