Merge pull request #97 from ethereum-optimism/blaine-readme-update

docs: installing just as part of dependencies.

README.md

@@ -13,6 +13,8 @@ This repository contains the [Specs Book](https://static.optimism.io/specs).
 
 ## Contributing
 
+We welcome your contributions. 
+
 ### Dependencies
 
 **Rust Toolchain**
@@ -27,6 +29,12 @@ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
 cargo install mdbook mdbook-katex mdbook-linkcheck mdbook-mermaid
 ```
 
+**`just` [installation](https://github.com/casey/just?tab=readme-ov-file#installation)**
+
+```sh
+brew install just
+```
+
 ### Serving the book locally
 
 ```sh