Add pointer to example programs in the docs

[rachitnigam]

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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 (#1474)
5. Producer-Consumer (#1496)

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