Allow features to require optional permissions

Design doc:
https://docs.google.com/document/d/1OhL0Yh7SmWffXyjW_XVQOK95Fqh7gLltk1eEtnKN8Ds/edit

Fixed: twpowertools:86
Change-Id: Iccb22aac2b285307854b7a4c002e9702c24d57f2
diff --git a/package.json b/package.json
index aab39ac..3263d41 100644
--- a/package.json
+++ b/package.json
@@ -34,6 +34,7 @@
     "style-loader": "^3.2.1",
     "webpack": "^5.44.0",
     "webpack-cli": "^4.7.2",
+    "webpack-preprocessor-loader": "^1.1.4",
     "webpack-shell-plugin-next": "^2.2.2"
   },
   "private": true,