Display showcase on rust-embedded.org landing page

[eldruin]

I think we could show more interesting content in the main landing page, currently containing a placeholder rust-embedded.org.

I propose displaying the showcase.

The showcase contains cool/motivational examples as well as links to docs.rust-embedded.org. Maybe we could add a link to the GH org since we have more of a project description there. Currently the showcase only has a link to the awesome-embedded-rust list.

Opinions?