chore: tsconfig paths for test - TS2307 Cannot find module in IDE (#550)

# Motivation

Don't know for VS Code but, Webstorm has issue resolving `*.svelte`
component when the import used `$lib/`. It seems it cannot inherits the
`path` defined in `"./.svelte-kit/tsconfig.json"` despite the extension
of the configs. I would guess the issue is related to Webstorm having
issue resolving relative paths.

# Changes

- Add `paths` to `tsconfig.spec.json`.

# Error

> TS2307: Cannot find module $lib/ components/ Back. svelte or its
corresponding type declarations.

<img width="1470" alt="Capture d’écran 2024-12-10 à 08 41 02"
src="https://github.com/user-attachments/assets/6ce4167e-650c-444f-8106-390761ab4db2">

tsconfig.spec.json

@@ -1,7 +1,13 @@
 {
   "extends": "./tsconfig.json",
   "compilerOptions": {
-    "types": ["vitest/globals"]
+    "types": ["vitest/globals"],
+    "paths": {
+      "$docs": ["./src/docs"],
+      "$docs/*": ["./src/docs/*"],
+      "$lib": ["./src/lib"],
+      "$lib/*": ["./src/lib/*"]
+    }
   },
   "exclude": [],
   "include": [