Write a document that describes API patterns we use in the design system

[nlopin]

The idea is to have some guidelines :

• what is considered a variant
• where we attach refs
• where do we spread props
• how we deal with aria attributes
• etc

This issue will be a collection of patterns that we then process and wrap into a document.

@lukahartwig @snapsnapturtle @duranmla please, bring your ideas

[nlopin]

Ref rule

• ref should be attached to the most obvious component. For example, for Input to <input>, for Checkbox to <input type="checkbox">
• if there is more than one "obvious" or "expected" place to add ref, there should be no ref prop, but custom ref prop for each place. For example, for Datepicker that selects a time period contains should have two refs fromRef and toRef