/usr/share/cairo-dock/gauges/Battery-Mono/readme is in cairo-dock-plug-ins-data 3.3.99.beta1.2.really.3.3.2-0ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 | Official Ubuntu-Mono's Icons assembled by Matttbe for Cairo-Dock.
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