Thermal design system

Use Vue components everywhere to build the application from a small button to a diff preview component.

Split the components into a separate package so it can be used across Thermal ecosystem _(Application, Website, and Marketing)_.

### Questions

- Should we style the components inline or in separate `.sass` file?
- How to name component and props?
- Is it the best way to use mixins for [spacing](https://github.com/gitthermal/thermal/blob/master/src/renderer/mixins/spacingProps.js), [font](https://github.com/gitthermal/thermal/blob/master/src/renderer/mixins/fontProps.js) and [border](https://github.com/gitthermal/thermal/blob/master/src/renderer/mixins/borderProps.js)?
- How can we leverage sass variables in Vue components?

## PRs

- [x] #111 `TModal` Modal component
- [x] #115 `TScrollbar` Scrollbar Layout
- [x] #125 `TButton` Button component
- [x] #128 `TFlexbox` Flexbox Layout
- [x] #137 `TContainer` Container Layout
- [ ] `TSwitch` Switch component
- [ ] `TLink` Link component
- [ ] `TText` Text component
- [ ] `TIcon` Icon component
- [ ] `TInput` Input component
- [ ] `TRadio` Radio component
- [ ] `TImage` Image component
- [ ] `TTag` Tag component
- [ ] `TDropdown` Dropdown component
- [ ] `TNotification` Notification component
- [ ] `TTooltips` Tooltips component
- [ ] Default color provider

## References

* https://github.com/gitthermal/thermal/issues/38

_We are looking for a more modular way to define and use Vue components for the long term, if you have any feedback or suggestion, 🙏🏻 please drop them in the comment section below._