Add pointer to example programs in the docs

[rachitnigam]

We have a growing collection of example that demonstrate various capabilities in Calyx. For example:

1. Pipelining of dynamic components using invoke
2. Reasoning about static timing
3. Synchronization
4. Arbitration (Tutorial: toy arbitration logic #1474)
5. Producer-Consumer (Producer consumer example using ref cells #1496)

We should add a link from the introduction docs to these examples so we can show off Calyx features to people!