docker: add /app to $PATH (#424)

Make it so llama-server can be called directly instead of with the full
path at /app/llama-server.

Fixes #423
Ref: #233

docker/llama-swap.Containerfile

@@ -29,6 +29,10 @@ RUN chown --recursive $UID:$GID $HOME /app
 USER $UID:$GID
 
 WORKDIR /app
+
+# Add /app to PATH
+ENV PATH="/app:${PATH}"
+
 RUN \
     curl -LO "https://github.com/${LS_REPO}/releases/download/v${LS_VER}/llama-swap_${LS_VER}_linux_amd64.tar.gz" && \
     tar -zxf "llama-swap_${LS_VER}_linux_amd64.tar.gz" && \