Plugin battery_: convert documentation to perlpod format

plugins/battery/battery_

@@ -1,15 +1,35 @@
 #! /bin/sh
-# Plugin to monitor the battery status via the uevent API
+
-#
+: <<=cut
-# (c) 2015 - GPLv2 - steve.schnepp@pwkf.org
+
-#
+=head1 NAME
-# It is a wildcard plugin, symlink it with the battery directory
+
-# default is to display charge as mAh, but you can also use percentage if you
+battery_ - monitor battery status via the uevent API
-# prefer, by setting the env var "percent" to "yes".
+
-#
+
-# [battery_*]
+=head1 CONFIGURATION
-# env.percent no
+
-#
+It is a wildcard plugin, symlink it into the plugins directory.
+
+ [battery_*]
+ env.percent no
+
+By default the charge current is displayed as mAh, but you can also use percentage if you
+prefer, by setting the environment variable "percent" to "yes".
+
+
+=head1 AUTHORS
+
+Copyright 2015 Steve Schnepp <steve.schnepp@pwkf.org>
+
+
+=head1 LICENSE
+
+GNU Library General Public License v2 only
+
+SPDX-License-Identifier: GPL-2.0-only
+
+=cut
 
 battery_name=${0##*_}
 percent=${percent:-"no"}