[Feature] Include template file in local folder

[Kourai]

Is your feature request related to a problem? Please describe.
I have several dashboard, but I'm using one single navbar to navigate in between
But as I'm using UI dashboard, I cannot include a single file for my navbar-template, so I need to copy-paste in each dashboard.

Describe the solution you'd like
I'd like to be able to have a single file containing my template, so I can do all the modifications in the same place

Additional context
I'm also using https://github.com/brunosabot/streamline-card. So I try writting my navbar in streamline, but it raise a lot of error, so it's a no go as a solution.
BUT I think maybe the streamline card code can provide some way to implant the "navbar template file" : with this integration, if you use yaml mode for your dashboard, you get to create some file for your template. But if you use UI dashboard, you can put all your streamline template in a single file /config/www/community/streamline-card/streamline_templates.yaml and it can be load in the UI dashboard !
I'd love to be able to do the same with navbar, using a file like /config/www/community/lovelace-navbar-card/navbar_templates.yaml where I'll be able to put my template !

[joseluis9595]

I'll take a look at this approach. Navbar-card templates are one of the most confusing aspects of its configuration. Having the ability to store the template in a separate file that can be read by any dashboard in HA might really well solve those issues!