Add just command runner to Neovim container (#55)

## Summary
Added the `just` command runner to the Homebrew packages installed in
the Neovim container.

## Changes
- Added `just` to the list of Homebrew packages in the container build
configuration
- `just` is a handy way to save and run project-specific commands,
similar to `make` but with a more modern syntax

## Details
The `just` tool is being added alongside other utility tools like `eza`,
`bat`, `yq`, and `jq` in the container's Layer 3 (Homebrew utilities).
This provides developers with access to command runners within the
containerized Neovim environment.

Co-authored-by: Claude <noreply@anthropic.com>

Author: binarypie

dot_files/nvim/Containerfile

@@ -92,7 +92,8 @@ RUN brew install \
     jq \
     yq \
     bat \
-    eza
+    eza \
+    just
 
 # =============================================================================
 # LAYER 4: Languages via Homebrew