Improvements on simpledev, live-server, etc

[maxmarkus]

Improvements after #1449, followup of #1565

[ndricimrr]

Should we get rid of babel.config.js or part of it 🤔 ?

[ndricimrr]

Some notes I pulled while looking at this in general. Probably helpful to keep track of why we changed it for future reference.

Removed Parts:

1. babel

2. core-js

3. regenerator-runtime

4. terser

5. live-server

History of removed parts:

1. babel , core-js and regenerator-runtime were first added in the same PR Svelte 3 migration as follows:

   • babel is added link:

   • regenerator-runtime is added link:

   • core-js is added link :

2. Terser is introduced later in the Improve js bundle size PR here

3. In same PR some slight modifications to babel by adding source-map option as inline

4. live-server : replaced with webpack-dev-server reason is here

Some results so far

There seem to be changes in bundle sizes:

• JS bundle size before:
  

• JS bundle size after:
  

Before and after images from bundle analysis:

Diff in size ≈ -100 KB

Also, due to removing babel build configs, luigi.js.map file which is ≈ 980 KB is also omitted from the resulting build. As it's needed for source mapping (i.e: better debugging) might consider adding source mapping through webpack's devtool as an alternative. Could help to consider this article to argue with.

On a side note need to discuss more about unsafe-inline

[hardl]

Please revert all changes that are not related to the fix of the corresponding ticket, e.g. live-server, prettier, etc.

[CLAassistant]

All committers have signed the CLA.

[maxmarkus]

I am creating a new PR, this one stays and will be merged afterwards with followup improvements.

[maxmarkus]

This implementation has some side effects and it was for the purpose of allowing CSP in dev mode.