TASK: Modernize code and bump dependencies

[Sebobo]

What has changed:

• Use latest React, TypeScript, Parcel, etc...
• Target modern browsers
• Reduce bundle size from 450KB to 350KB
• Require at least Neos 7.3 and PHP 7.3
• Use yarn workspaces
• Use "Lite" stylesheet from Neos
• Adjust resource inclusion setting to allow additional resources via settings
• Update linting and resolve issues
• Apply PHP code cleanup hints to controller

[Sebobo]

We should define a new minor version when this is released as it's not breaking but has bumped dependencies.

[Sebobo]

The largest part of the bundle are react-com and the react-datepicker. I don't know right now how to reduce this further.

[jonnitto]

Tested it and it works

[ahaeslich]

The linter check fails in _add-redirect-form.css on line 59. The import of @import "../vendor/datepicker"; seems a bit odd.

@Sebobo can we delete this or do we have to include something else?

[crydotsnake]

Sorry for my missing review so far. Will take a look at the PR this evening!

[crydotsnake]

Tested, and it works!

[Sebobo]

The linter check fails in _add-redirect-form.css on line 59. The import of @import "../vendor/datepicker"; seems a bit odd.

@Sebobo can we delete this or do we have to include something else?

There was a reason due to specificity. So I disabled the style lint rule.