chore: turn on preserveConstEnums so we export const enum properly

Long Ho · Long Ho · commit 61117187eb4d · 2020-03-21T00:00:31.000-04:00
diff --git a/tsconfig.json b/tsconfig.json
@@ -9,6 +9,7 @@
         "resolveJsonModule": true,
         "noUnusedLocals": true,
         "noUnusedParameters": true,
+        "preserveConstEnums": true,
         "types": [
             "babel__core",
             "babel__generator",
