docs: Added other ENV variables available (#85)

Author: mateuszgachowski

docs/guide/env.md

@@ -10,10 +10,22 @@
 
 ## With the GraphQL server enabled
 
+- **`VUE_APP_GRAPHQL_HOST`**
+
+  Hostname of GraphQL API Server, default: `localhost`
+
+- **`VUE_APP_GRAPHQL_PATH`**
+
+  Path on which to serve graphQL, defaultL `/graphql`
+
 - **`VUE_APP_GRAPHQL_PORT`**
 
   Port of the GraphQL API Server, default: `4000`
 
 - **`VUE_APP_APOLLO_ENGINE_KEY`**
 
   API key for [Apollo Engine](https://engine.apollographql.com)
+
+- **`VUE_APP_GRAPHQL_SUBSCRIPTIONS_PATH`**
+
+  Subscriptions path, default: `/graphql`