Optimize dependency management and resolve build warnings

[harej]

When npm run build is run, four warnings are produced:

WARNING in ./node_modules/codemirror/addon/mode/loadmode.js 53:6-19
Critical dependency: the request of a dependency is an expression
 @ ./src/editor.js 25:0-40
 @ ./src/index.js 3:0-5:28 11:0-14 12:0-16 13:0-8 16:0-21 17:0-13

WARNING in asset size limit: The following asset(s) exceed the recommended size limit (244 KiB).
This can impact web performance.
Assets:
  bundle.js (1.44 MiB)

WARNING in entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.
Entrypoints:
  main (1.52 MiB)
      main.css
      bundle.js


WARNING in webpack performance recommendations:
You can limit the size of your bundles by using import() or require.ensure to lazy load some parts of your application.
For more info visit https://webpack.js.org/guides/code-splitting/

This points to unoptimized code that could affect performance for the end-user.

Criteria to resolve issue

The issue will be considered resolved when there are no more warnings during the build process.