get /templates request takes a long time

[bartcuijpers]

When requesting templates using http://[server]:8000/templates, the request takes about 4 seconds.

[Julusian]

This is expected currently. While the scanner is pregenerating details about media, it is scanning the templates folder for each request made.
We will happily accept a PR which changes this to do the proper scanning flow, based upon the existing media flow