Add Home Assistant Custom Component to HACS

[OliverCullimore]

Make the custom component installable via HACS.

The docs here detail what's necessary to do for this.

As a start, I'll submit a PR to add the hacs.json file and README instructions for installing via the HACS custom repositories method.

Ideally, we eventually could submit for this to be included in the HACS default repository making installation via HACS as simple as just searching for the component and clicking download.

[robbrad]

FYI @OliverCullimore https://github.com/hacs/default/pull/2255

[robbrad]

Pending HACS