[enhancement] Parsing .mustache file as .html

[drypatrick]

Hi, and thanks for this wonderful plugin.
I would like to ask if would be possible to extend the minify functionality to the .mustache file, since they have the same feature of a standard html file.
Just saving with .html extension lets the plugin do it's job, but it's pretty boring to changhe the extension each time.

Thanks, bye!

[kendfss]

There's a few ways to do this. Perhaps the easiest is to change

    "allowed_file_types": [
        "css",
        "js",
        "json",
        "html",
        "svg"
    ],

into:

    "allowed_file_types": {
        "html": [".mustace"],
        "js": ["js", "ts"],
        // etc
    }

But this would mean changing the semantics of allowed_file_types to be applicable outside the context of acting on saves

Another way is to implement via #89
The easy(?) way to do this is by allowing:

"aliases": [".this", "that", "and", "the", ".other"]

as an option for each extension

Another way of doing that would be to simply add a new extension with the following option:

"mustache": {
  "syntax": "html"
}

This would allow you to get more specific with how you want to handle this extension