[PM-22629] Forbid importing popup outside (#15168)

Adds an eslint rule forbidding non popup scripts from importing popups. Also added a webpack plugin that throws if it detects @angular inside background output.

apps/browser/webpack/angular-check.js

@@ -0,0 +1,21 @@
+/**
+ * Webpack plugin that errors if it detects angular imports.
+ */
+class AngularCheckPlugin {
+  apply(compiler) {
+    compiler.hooks.assetEmitted.tap("AngularCheckPlugin", (file, info) => {
+      // Ensure we only check outputted JavaScript files
+      if (!file.endsWith(".js")) {
+        return;
+      }
+
+      if (info.content.includes("@angular")) {
+        throw new Error(
+          `Angular detected in ${file}. Please ensure angular is not imported to non popup scripts.`,
+        );
+      }
+    });
+  }
+}
+
+module.exports = AngularCheckPlugin;