Automatic template loading for dashboards created in the GUI

[neponn]

Checklist

• I am running the latest version of the card
• I checked if there isn't another feature request opened with the same request
• I checked that the feature is not already available in the dev branch

Is your feature request related to a problem? Please describe.
I'm a long time apexcharts-card user, and have made extensive use of templates to keep my charts looking consistent (and make them easy to build). Most of my dashboards are YAML based, but I'm making the transition to GUI based dashboards. Right now, there is no easy way to access templates from the visual editor other than copy / pasting into the raw YAML at the top of each dashboard. This gets old fast.

Describe the solution you'd like
It would be great if apexcharts-card had a known location that could act as an anchor for templates. For example:

/config/www/apexchart-templates/

When apexcharts-card is first loaded, it could check for the existence of this folder and do something akin to "!include_dir_merge_named /config/www/apexchart-templates/" to make templates available to apexcharts-cards created in the visual editor.

Describe alternatives you've considered
Of course, I can keep using YAML dashboards and / or pasting templates into the top of the raw YAML for GUI based dashboards. But it would be nice if there was a cleaner solution.

Additional context
This isn't my idea. I noticed this approach taken by streamline-card - described here (unfold Method 1 for the detail). It looks like a pretty smart approach to me.