Implement new async crawler features and stability updates

- Introduced new async crawl strategy with session management.
  - Added BrowserManager for improved browser management.
  - Enhanced documentation, focusing on storage state and usage examples.
  - Improved error handling and logging for sessions.
  - Added JavaScript snippets for customizing navigator properties.

crawl4ai/js_snippet/navigator_overrider.js

@@ -0,0 +1,25 @@
+// Pass the Permissions Test.
+const originalQuery = window.navigator.permissions.query;
+window.navigator.permissions.query = (parameters) =>
+    parameters.name === "notifications"
+        ? Promise.resolve({ state: Notification.permission })
+        : originalQuery(parameters);
+Object.defineProperty(navigator, "webdriver", {
+    get: () => undefined,
+});
+window.navigator.chrome = {
+    runtime: {},
+    // Add other properties if necessary
+};
+Object.defineProperty(navigator, "plugins", {
+    get: () => [1, 2, 3, 4, 5],
+});
+Object.defineProperty(navigator, "languages", {
+    get: () => ["en-US", "en"],
+});
+Object.defineProperty(document, "hidden", {
+    get: () => false,
+});
+Object.defineProperty(document, "visibilityState", {
+    get: () => "visible",
+});