- Update: Copy of core-js and qr-manipulation

- npm: Add `underscore` to copy script
- npm: Make `copy`, `compress-images`, `start-embedded`, `build-docs-remove`
  scripts cross-platform; add `start-allow-origin` script
- npm: Update devDeps/`package-lock.json`

.ncurc.js

@@ -0,0 +1,6 @@
+module.exports = {
+  "reject": [
+    // Old copy with jspdf which needs updating: https://github.com/SVG-Edit/svgedit/issues/51
+    "underscore"
+  ]
+};