update README documentation to specify just as optional instruction

Author: Hamza1610

README.md

@@ -17,7 +17,7 @@ Before building `bdkpython` locally, ensure you have installed the following too
 
 - **Rust toolchain (`rustup`)**: Required to compile `bdk-ffi`. Install from [rustup.rs](https://rustup.rs/).
 - **`uv`**: Fast Python package installer and resolver. Install from [Astral uv Docs](https://docs.astral.sh/uv/).
-- **`just`**: Command runner used for repo tasks. Install via `cargo install just` or your system package manager.
+- **`just` (optional)**: Command runner used for repo tasks. Install via `cargo install just` or your system package manager.
 - **Windows (C++ Build Tools)**: Install Visual Studio Build Tools with the *Desktop development with C++* workload (provides `link.exe` and MSVC toolchain required for `x86_64-pc-windows-msvc`).
 
 ## Local Testing and Usage