Add support for showing controller battery levels (where possible)

See: https://wiki.gentoo.org/wiki/Sony_DualShock#Battery_charge_level

It also appears that you can check battery levels with xow, at least according the screenshot on their github page.

Start by reading the linked Sony DualShock battery-level documentation and the xow reference, then locate the project's controller-status entry point. Define support for the controllers that expose battery data and verify that available levels are shown without breaking controllers where no level can be read.

Written by the indexing model from the issue text.