replace package.json scripts with just.

justfile

@@ -0,0 +1,19 @@
+export PATH := "./node_modules/.bin:" + env_var('PATH')
+
+install-dependencies:
+    yarn --ignore-engines
+
+deps-installed := `ls node_modules`
+
+install-and-build:
+    if deps-installed != "node_modules" { install-dependencies }
+    build
+
+build:
+    node build.js
+
+test: build
+    jest
+
+testOnly file: build
+    jest {{file}}