update readme

frontend/README.md

@@ -1,9 +1,20 @@
 # Planetwars frontend
 
+This is the main folder of the Planetwars frontend.
+Here you can compile the rust wasm files needed in the 'WWW' folder that is actually used to host the server.
+When making changes make sure you recompile them using `wasm-pack build`
+and webpack is running in www with `npm start` from the www folder.
+
+### Build
+
+wasm-pack build
+
 ### Dependencies
 
 - rustup, rustc, cargo
 - npm
+- wasm-pack
+- nightly, wasm32-unknown-unknown target
 
 ...