improve build scripts

- use shebang
- use pushd/popd
- add npm install to initialize node project dependencies

Software/MainBoard/rust/image_build.sh

@@ -1,12 +1,16 @@
+#!/usr/bin/env bash
+
 rm image.bin
 rm ./src/webserver/index.html.gz
 rm ./src/webserver/bundle.js.gz
 set -e
-cd ./src_webpack/
+
+pushd ./src_webpack/
+npm install
 npx webpack build
 cp index.html.gz ../src/webserver/index.html.gz
 cp bundle.js.gz ../src/webserver/bundle.js.gz
-cd ../
+popd
 
 set -e
 cargo build --release