plugins: refactory to use default export for new backend system

Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Co-authored-by: Camila Belo <camilaibs@gmail.com>
Co-authored-by: Johan Haals <johan.haals@gmail.com>
Co-authored-by: Philipp Hugenroth <philipph@spotify.com>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/proxy-backend/src/index.ts

@@ -21,4 +21,4 @@
  */
 
 export * from './service';
-export { proxyPlugin } from './plugin';
+export { proxyPlugin as default } from './plugin';