Add event handler props for components.

Use 100% for `<button>` element because it is auto-size by default.

Button, Select, and TextInput has now opt-in borders.

Include a section on theming.

Cover scenarios primarily for adjusted behavior on Button, as well as ensure components are exported correctly.

Migrate from GitHub, rewrite common components to TypeScript (main and test files). Also replaced Storybook to Docz.