add some developer documentation

DEVELOPING.md

@@ -0,0 +1,80 @@
+# Developing
+
+## Setup
+
+### Nix based development environment
+
+The recommended way to setup the development environment is to use
+[Lix](https://lix.systems/install/)/[Nix](https://nixos.org/download/).
+
+Once installed, you can enter the development shell using `nix develop` or,
+setup [direnv](https://direnv.net/) to automatically enter the development shell
+when you enter the folder.
+
+The development shell provides all necessary tooling to develop haze.
+
+### Without Nix
+
+The fooling tools need to be setup to develop without using Nix to manage the
+development setup:
+
+- [`cargo`](https://doc.rust-lang.org/cargo/getting-started/installation.html) -
+  For building the program
+- [`mdbook`](https://github.com/rust-lang/mdBook) - For building the
+  documentation
+- [`prettier`](https://prettier.io/) - For formatting the non-rust files
+- [`vale`](https://vale.sh/) - For checking documentation
+
+## Building
+
+```bash
+cargo build
+```
+
+The binary can then be found at `target/debug/haze`.
+
+## Formatting
+
+### With Nix
+
+```bash
+nix fmt
+```
+
+### Without Nix
+
+#### Rust code
+
+```bash
+cargo fmt
+```
+
+#### Documentation
+
+```bash
+prettier --write '**/*.md'
+```
+
+### Building documentation
+
+```bash
+mdbook serve
+```
+
+### Checking documentation
+
+```bash
+vale src/ book/src/ book/README.md *.md
+```
+
+### Run all checks
+
+```bash
+nix flake check
+```
+
+### Building docker images
+
+```bash
+nix run .#'"haze-image-php-8.4"'.copyToDockerDaemon
+```