Add secret and global state management + messaging between web and extension; persist API key and max num requests; add Welcome screen

src/shared/WebviewMessage.ts

@@ -1,5 +1,5 @@
 export interface WebviewMessage {
-    type: "text" | "action"
+    type: "text" | "action" | "apiKey" | "maxRequestsPerTask" | "webviewDidLaunch"
     text?: string
     action?: "newTaskButtonTapped" | "yesButtonTapped" | "noButtonTapped" | "executeButtonTapped"
 }