Improve scss alias handling

[mikeybinns]

This PR updates the existing scss aliases to include Launchpad, and also provides the ability to modify the scss aliases per project with a config file.

Example scssAliases.config.ts:

import type { SCSSAliases } from "@atomicsmash/cli";
import { pathToFileURL } from "node:url";
import { resolve } from "node:path";

export default {
  importers: [
    // Launchpad alias is already available, but this removes the sitecss alias to prevent usage.
    {
      findFileUrl(url) {
        if (!url.startsWith("launchpad:")) return null;
        const pathname = url.substring(10);
        return pathToFileURL(
          `${resolve(process.cwd(), "public/wp-content/themes/launchpad/src/styles")}${pathname.startsWith("/") ? pathname : `/${pathname}`}`,
        );
      },
    },
  ],
} satisfies SCSSAliases;

Example usage:

@use "launchpad:some-folder/partial";

[changeset-bot]

🦋 Changeset detected

Latest commit: 33a7304

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@atomicsmash/compiler	Minor
@atomicsmash/cli	Minor

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[MeMattStone]

Looks like a good addition to me