feat: restructure project and update documentation

plugins/storage.js

@@ -0,0 +1,31 @@
+/**
+ * SigPro Storage Plugin
+ * Automatically synchronizes signals with localStorage.
+ */
+export const Storage = ($) => {
+  /**
+   * Persists a signal's value in localStorage.
+   * @param {Function} $sig - The signal to persist.
+   * @param {string} key - The localStorage key name.
+   * @returns {Function} The same signal for chaining.
+   */
+  _storage = ($sig, key) => {
+    // 1. Initial Load: If there's data in storage, update the signal immediately
+    const saved = localStorage.getItem(key);
+    if (saved !== null) {
+      try {
+        $sig(JSON.parse(saved));
+      } catch (e) {
+        console.error(`[SigPro Storage] Error parsing key "${key}":`, e);
+      }
+    }
+
+    // 2. Auto-Save: Every time the signal changes, update localStorage
+    $(() => {
+      const val = $sig();
+      localStorage.setItem(key, JSON.stringify(val));
+    });
+
+    return $sig;
+  };
+};