I want to browse and add components to the end of the form using my keyboard

[pinussilvestrus]

Is your feature request related to a problem? Please describe.

I want to browse and add components to the end of the form using my keyboard. I have to use my mouse currently via drag and drop as keyboard is not supported. This blocks keyboard users to add new components to the form.

Describe the solution you'd like

Make browsing and adding form field components fully supported by keyboard.

Part of this was already sketched via #503 (comment) (branch: https://github.com/bpmn-io/form-js/tree/503-library-keyboard-support).

Describe alternatives you've considered

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Additional context

Related to #173
Related to #503 (comment)