Wear OS: Support MDI icons in Template tile

[slovdahl]

Is your feature request related to a problem? Please describe.

I woud like to create a simple "dashboard"-like template tile. Emojis can help to some extent in this regard, but there's a lot more MDI icons available for visualizing things.

Describe the solution you'd like

No strong opinion on how it would be done, but one way of doing it would be to support the <ha-icon icon='mdi:foo' /> HTML tag that can also be used in Lovelace.

Describe alternatives you've considered, if any

Use emojis built-in in Android.

Additional context

This is what my Template tile currently looks like:

[jpelgrom]

Comment from @dshokouhi in another issue relating to this:

For something like this we may need to pick something that is unique for the app to pick up on.

In my opinion we should avoid app specific extensions to Home Assistant's templating to prevent compatibility issues now or in the future.

[slovdahl]

So would a <ha-icon icon='mdi:foo' /> HTML tag be a sane way of doing it? 🤔

[dshokouhi]

In my opinion we should avoid app specific extensions to Home Assistant's templating to prevent compatibility issues now or in the future.

I agree however it seems this may already have been thought of by others 😃

So would a <ha-icon icon='mdi:foo' /> HTML tag be a sane way of doing it? 🤔

Given that it is listed in the user facing documentation I think it may actually be a good way forward?

https://www.home-assistant.io/dashboards/markdown/#icons