Update system-info macOS user agent

Add CPU temperature to `status-info`, conditionally display battery
charge percentage, and documents the commands.

.conduit.yaml

@@ -10,6 +10,7 @@
     - tmux
     - urlview
     - reattach-to-user-namespace
+    - osx-cpu-temp
 - pacman:
     - tmux
     - xclip

system-info/system-info-macOS.sh

@@ -12,8 +12,18 @@ fi
 trap '[ -f $cache_file ] && rm $cache_file; exit' INT
 trap '[ -f $cache_file ] && rm $cache_file; exit' TERM
 
+# Check if a battery is installed.
+ioreg -w0 -l | grep BatteryInstalled &> /dev/null && \
+  has_battery=true || has_battery=false
+
 while true; do
-  battery="`pmset -g batt | grep --color=never -Eo '\d+%'` ↯"
-  echo "$battery" > $cache_file
+  # Get the current CPU temperature.
+  cpu_temp="`/usr/local/bin/osx-cpu-temp`"
+  # Parse the current battery charge percentage.
+  $has_battery && \
+    battery=" `pmset -g batt | grep --color=never -Eo '\d+%'` ↯"
+  # Write to the cache file.
+  echo "$cpu_temp$battery" > $cache_file
+  # Don't spin, sleep instead.
   sleep 2
 done