Migrate from snowpack to webpack

[jonandernovella]

Reason for this PR

The snowpack project is not under active maintenance any longer so it's a good idea to switch to a widely adopted tool such as webpack.

Type of change

• New feature (non-breaking change which adds functionality)

List of changes made

• Producttion build works with webpack
• Dev server with hot reload powered by webpack

Testing

1. Bring down all containers and volumes
2. Update your env accordingly
3. Build prod or dev setup
4. Start the services and navigate to localhost:4567
5. Test updating the css code and see if HR works

Definition of Done checklist

• I have made an effort making the commit history understandable
• I have performed a self-review of my own code and commented any hard-to-understand areas
• Tests and lint/format validations are passing
• My changes generate no new warnings

[HenrikeW]

The build works smoothly, and so does the hot reload. But parts of the CSS broke on the way, compare mostly the footer in the two screenshots. First the branch from this PR, below the current develop branch.
No idea so far what can have caused this.

[HenrikeW]

Now it looks like it did before, nice!

[jonandernovella]

The build should be much smaller now. I have tested both the dev and production setup and they are working well.