custom flag (2) (#1303)

## Description:

This PR implements the permission check logic.

Other related parts will be handled in a separate UI update.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

src/core/PatternDecoder.ts

@@ -1,5 +1,3 @@
-import { base64url } from "jose";
-
 export class PatternDecoder {
   private bytes: Uint8Array;
 
@@ -7,8 +5,11 @@ export class PatternDecoder {
   readonly width: number;
   readonly scale: number;
 
-  constructor(base64: string) {
-    this.bytes = base64url.decode(base64);
+  constructor(
+    base64: string,
+    base64urlDecode: (input: Uint8Array | string) => Uint8Array,
+  ) {
+    this.bytes = base64urlDecode(base64);
 
     if (this.bytes.length < 3) {
       throw new Error(