Allow user defined functions capability

[septs]

Allow hugo define hugo-specific built-in sass functions

Improve development experience (simplify reference resource files)

Replaced by https://github.com/bep/golibsass/issues/7

https://github.com/bep/godartsass/blob/9f9f1c1aeb19fa45147bf1ca123e73a8dec85e66/internal/embeddedsass/embedded_sass.proto#L537-L568

https://github.com/bep/godartsass/blob/9f9f1c1aeb19fa45147bf1ca123e73a8dec85e66/internal/embeddedsass/embedded_sass.proto#L220-L239

[septs]

https://github.com/sass/embedded-host-node/blob/main/lib/src/function-registry.ts

https://github.com/sass/embedded-host-node/blob/master/lib/src/compile.ts#L121

https://github.com/sass/embedded-host-node/blob/master/lib/src/compile.ts#L154

[septs]

i want use sass function, improve developer experience

port resources series api into sass compiler, simplify use image file steps

[bep]

port resources series api into sass compiler, simplify use image file steps

Next Hugo allows you pass the URL of these image resources as variables to Dart Sass. How is your suggested approach better? To me it sounds

• Like a very tight coupling between the stylesheet and Hugo's API
• A fairly ineffective way of doing it compared to just passing in some string values on Execute

[bep]

Note, that I don't mind adding a "functions API" to this library as long as someone could

• Give me one or more great use cases for it.
• Suggest a good implementation.

[septs]

.example {
  --use-file-with-function: resources-get(file-path); // intuitive
  // vs
  --use-file-with-variable: $injected-file-name; // define separation
}

[bep]

• resources-get(file-path): needs Hugo to work, designer needs to understand Hugo's API, will cost one RPC invocation, is hard to reason about re cache busting.
• $injected-file-name: can be defined by Hugo or a stylesheet, is easy to reason about re. cache busting