docs: document shared library

readme.md

@@ -104,17 +104,30 @@ As far as tested, the operating systems under are supported:
 -   MacOS
 -   Windows 11 and WSL
 
-## Development
+## Contributing
+
+Carbonyl is split in two parts: the "core" which is built into a shared library (`libcarbonyl`), and the "runtime" which dynamically loads the core (`carbonyl` executable).
+
+The core is written in Rust and takes a few seconds to build from scratch. The runtime is a modified version of the Chromium headless shell and takes more than an hour to build from scratch.
+
+If you're just making changes to the Rust code, build `libcarbonyl` and replace it in a release version of Carbonyl.
+
+### Core
+
+```console
+$ cargo build
+```
+
+### Runtime
 
 Few notes:
 
--   You need to build Chromium
--   Building Carbonyl is almost the same as building Chromium with extra steps to patch and bundle the Rust library. Scripts in the `scripts/` directory are simple wrappers around `gn`, `ninja`, etc..
+-   Building the runtime is almost the same as building Chromium with extra steps to patch and bundle the Rust library. Scripts in the `scripts/` directory are simple wrappers around `gn`, `ninja`, etc..
 -   Building Chromium for arm64 on Linux requires an amd64 processor
 -   Carbonyl is only tested on Linux and macOS, other platforms likely require code changes to Chromium
 -   Chromium is huge and takes a long time to build, making your computer mostly unresponsive. An 8-core CPU such as an M1 Max or an i9 9900k with 10 Gbps fiber takes around ~1 hour to fetch and build. It requires around 100 GB of disk space.
 
-### Fetch
+#### Fetch
 
 > Fetch Chromium's code.
 
@@ -122,7 +135,7 @@ Few notes:
 $ ./scripts/gclient.sh sync
 ```
 
-### Apply patches
+#### Apply patches
 
 > Any changes made to Chromium will be reverted, make sure to save any changes you made.
 
@@ -130,7 +143,7 @@ $ ./scripts/gclient.sh sync
 $ ./scripts/patches.sh apply
 ```
 
-### Configure
+#### Configure
 
 ```console
 $ ./scripts/gn.sh args out/Default
@@ -165,7 +178,7 @@ import("//carbonyl/src/browser/args.gn")
 # symbol_level=0
 ```
 
-### Build binaries
+#### Build binaries
 
 ```console
 $ ./scripts/build.sh Default
@@ -179,7 +192,7 @@ This should produce the following outputs:
 -   `out/Default/libGLESv2.so`
 -   `out/Default/v8_context_snapshot.bin`
 
-### Build Docker image
+#### Build Docker image
 
 ```console
 # Build arm64 Docker image using binaries from the Default target
@@ -188,7 +201,7 @@ $ ./scripts/docker-build.sh Default arm64
 $ ./scripts/docker-build.sh Default amd64
 ```
 
-### Run
+#### Run
 
 ```
 $ ./scripts/run.sh Default https://wikipedia.org