Add env variable documentation

client/README.md

@@ -1,3 +1,5 @@
-# react-parcel-boilerplate
+## Configuration
 
-A minimal react boilerplate that uses parcel to bundle all of your assets
+To configure the client, you need these fields in your `.env` file:
+
+* API_BASE_PATH - Backend URL

server/README.md

@@ -0,0 +1,6 @@
+## Configuration
+
+To configure the server, you need these fields in your `.env` file:
+
+* AUTH_SECRET - Secret used to sign JWTs
+* DATABASE_URL - Database path