Documentation: Add links to src

[michaelx]

New Feature Proposal

Description

The documentation website should have a "go to source" link per component, e.g. https://precise-ui.io/#/Components/Modal should have a link to https://github.com/ZEISS/precise-ui/tree/develop/src/components/Modal.

Background

This should make it easier for developers to pick-up Precise UI, as their UI library, and might also increase contributions.