Update the "hacking" section of the documentation (#19)

doc/src/hacking.md

@@ -14,6 +14,9 @@ Experimental features "nix-command" and "flakes" need to be enabled in your Nix
 configuration for the server to run properly. Nix >= 2.18 is also required but
 it is provided by the Nix shell.
 
+The following instructions assume that you are inside the Nix development
+environment.
+
 ## Dependencies
 
 Typhon uses [Actix](https://actix.rs/) for the web server and
@@ -22,23 +25,31 @@ with [Leptos](https://leptos.dev/). Typhon is built with `cargo-leptos`.
 
 ## Building
 
-To build Typhon, go to the root of the project and run:
+If you are building Typhon for the first time, first go to
+`typhon-webapp/assets` and run `npm install`.
+
+Then, to build Typhon, go to the root of the project and run:
 
 ```shell
-nix-shell --run build
+build
 ```
 
 ## Testing
 
-To run Typhon, create `/nix/var/nix/gcroots/typhon/` and make sure that you
-have write access to the directory. Then go to the root of the project and run:
+To run Typhon, create `/nix/var/nix/gcroots/typhon/` and make sure that you have
+write access to the directory. Then go to the root of the project and run:
 
 ```shell
-nix-shell --run serve
+serve
 ```
 
 The server will be available at `http://localhost:3000`, the admin password is
 empty.
 
-You can also run `nix-shell --run watch` to re-compile the server automatically
-at each modification of the code.
+You can also run `watch` to re-compile the server automatically at each
+modification of the code.
+
+## Formatting
+
+Before submitting changes to Typhon, be sure to format the code using the
+`format` command.