Spike: Plugin/extensibility for designer/model/runner

[jenbutongit]

Is your feature request related to a problem? Please describe.
Some departments may want to extend the form builder from an external application, i.e. add additional text field components.

Describe the solution you'd like
A way of specifying additional component, service, page etc files that can be imported and used dynamically.

Describe alternatives you've considered
N/A

Additional context
N/A

[developerbuzz]

We have built an adapter model for xGovFormBuilder at MHCLG for this purpose. We have a number of components we use for funding that aren't covered by the original version. Give me a shout if you want to talk it through.