add form, textinput and sample form components

[katjad]

Mini form with just text input field can be seen at http://localhost/admin - submitting logs input to console

[AlisonYoon]

great!

[fourstacks]

Looks good @katjad!

We might have to give some thought as to approach we take to authoring React components - whether to use class-based components or hook-based components. Personally I'd opt for hook-based as that's what the React core team are pushing these days but more than anything else it will help for consistency in the project if we stick to one convention.

Either way - let's merge this in for now - we can always revisit it later.