Suggestion: load button templates from local yaml file

I've been using the excellent [Streamline Card](https://github.com/brunosabot/streamline-card) recently, and their implementation of templates is similar to this repo in their structure (defined within the lovelace raw yaml). However, this is a request to shamelessly borrow their template loading from local YAML files. Primary motivation here is the ability to have one set of button card templates across multiple dashboards. I've been able to do this with streamline card by simply creating a "streamline-card.yaml" file within `/www/community/streamline-card/` and have it automatically requested as part of the loading of the add-on. I now am able to edit a single file and have it update every instance of that template This would massively simplify both the editing (not needing to be done within the lovelace raw editor) and management of large numbers of templates - particularly if able to extend this via !includes within the local YAML file itself