feat(plex): add support for custom Plex Web App URLs (#1581)

* feat(plex): add support for custom Plex Web App URLs

* refactor: clean up Yup validation in *arr modals & email settings

* fix(lang): change Web App URL tip

* fix: remove web app URL validation and add 'Advanced' badge

overseerr-api.yml

@@ -171,6 +171,9 @@ components:
           readOnly: true
           items:
             $ref: '#/components/schemas/PlexLibrary'
+        webAppUrl:
+          type: string
+          example: 'https://app.plex.tv/desktop'
       required:
         - name
         - machineId