Package support

It would be nice to be able to use this without people having to check out the repo with Git using the command line. That might be a barrier to entry for less technical users.

I have been playing around with packages, and so far it looks like everything works except for AQI≥501.png, which is hard-coded to the packages/haks/ directory. Despite the docs (and source code) saying this is a relative path compared to the YAML file, it is relative to the root YAML, not the YAML containing the call.

Besides that one roadblock, the rest is working about as expected. Been playing in the remote_package_test branch.

I have a bad workaround: hard-code the .esphome/packages/<hash>/ directory for the image. The hash comes from the URL and ref of the package, so that would only work on the main branch and if they use the exact URL to check it out. So not ideal.