[experimental]: Implement the initial, extendable toolbar core #427

In order to have an extendable toolbar to register the nodes we should create a core package.

Acceptance Criteria

• It can be used as an independent tool, if needed
• It must be framework independent
• It must have adapters for different frameworks
• Toolbar node registration API is documented

Notes

HWPToolkit should house the generic Toolbar, without strong opinions. Framework adapters from Faust.js would adjust the toolbar to best work for each corresponding framework.

Dependent on #428