dev: add missing constructors to new puter.js methods

- Also add subscribe() to threads module so I don't lose it in a git
  stash

src/puter-js/src/modules/Perms.js

@@ -1,4 +1,8 @@
 export default class Perms {
+    constructor (context) {
+        this.authToken = context.authToken;
+        this.APIOrigin = context.APIOrigin;
+    }
     setAuthToken (authToken) {
         this.authToken = authToken;
     }

src/puter-js/src/modules/Threads.js

@@ -1,4 +1,8 @@
 export default class Threads {
+    constructor (context) {
+        this.authToken = context.authToken;
+        this.APIOrigin = context.APIOrigin;
+    }
     setAuthToken (authToken) {
         this.authToken = authToken;
     }
@@ -44,4 +48,8 @@ export default class Threads {
             options ?? {},
         );
     }
+
+    async subscribe (uid) {
+        puter.fs.socket.emit('thread.sub-request', { uid });
+    }
 }