UPDATE: the new Svelte FAQ now has this info in it (though I go into a little more detail here in case you're curious)

UPDATE 2: Updated examples to match the latest version of SvelteKit

Don't want to do relative imports (../../stores/user) and instead want to rock some sexy absolute imports ($stores/user)?

Well you're in luck because, with SvelteKit, you can add as many custom module import aliases as you want.

In this (very short) tutorial, I'm going to add two aliases, one for my src/components directory (which I'm renaming from src/lib because reasons) and adding src/stores for, well, my stores. Let's go! 🏃‍♀️

Add aliases to `svelte.config.cjs`

Add any aliases you want in your svelte.config.cjs file at the root of your project. We will add a resolve object to kit.vite.resolve with an object of our aliases.

Here is the approximate diff you should see when you're done:

import preprocess from 'svelte-preprocess';
+ import { resolve } from "path";

/** @type {import('@sveltejs/kit').Config} */
const config = {
    // Consult https://github.com/sveltejs/svelte-preprocess
    // for more information about preprocessors
    preprocess: preprocess(),

    kit: {
        // hydrate the <div id="svelte"> element in src/app.html
-       target: '#svelte'
+       target: '#svelte',
+       vite: {
+           resolve: {
+               alias: {
+                   $components: resolve('./src/components'),
+                   $stores: resolve('./src/stores'),
+                   $actions: resolve('./src/actions')
+               }
+           }
+       }
    }
};

export default config;

Now you should be able to import your stuff from anywhere using your new aliases, like:

import Counter from '$components/Counter'
import { user } from '$stores/auth'

Obviously you can add as many as you want and can also link to directories other than src. Have at it!

Adding Typescript aliases

If you're using Typescript, make sure to update your tsconfig.json with your aliases so they match that of your svelte.config.cjs:

{
    "compilerOptions": {
        "moduleResolution": "node",
        "module": "es2020",
        "lib": ["es2020"],
        "target": "es2019",
        /**
            svelte-preprocess cannot figure out whether you have a value or a type, so tell TypeScript
            to enforce using \`import type\` instead of \`import\` for Types.
            */
        "importsNotUsedAsValues": "error",
        "isolatedModules": true,
        "resolveJsonModule": true,
        /**
            To have warnings/errors of the Svelte compiler at the correct position,
            enable source maps by default.
            */
        "sourceMap": true,
        "esModuleInterop": true,
        "skipLibCheck": true,
        "forceConsistentCasingInFileNames": true,
        "baseUrl": ".",
        "allowJs": true,
        "checkJs": true,
        "paths": {
-           "$lib/*": ["src/lib/*"]
+           "$components/*": ["src/components/*"],
+           "$stores/*": ["src/stores/*"],
+           "$actions/*": ["src/actions/*"]
        }
    },
    "include": ["src/**/*.d.ts", "src/**/*.js", "src/**/*.ts", "src/**/*.svelte"]
}