add section 'examples and projects' listing repos using Sonobe

src/SUMMARY.md

@@ -15,3 +15,4 @@
 - [Design](design/design.md)
 	- [Nova+CycleFold circuit](design/novacyclefold-circuit.md)
 	- [Decider Onchain](design/nova-decider-onchain.md)
+- [Examples and Projects](examples_projects.md)

src/examples_projects.md

@@ -0,0 +1,5 @@
+# Examples and Projects
+
+> This section contains examples and projects that use Sonobe. You can find isolated examples too in the dir [sonobe/examples](https://github.com/privacy-scaling-explorations/sonobe/tree/main/examples).
+
+- [https://github.com/dmpierre/sonobe-btc](https://github.com/dmpierre/sonobe-btc): implementation of an on-chain Bitcoin light client leveraging Sonobe: uses nova to verify bitcoin's proof of work over 100k blocks and verify the zkSNARK IVC proof on chain.