Add a link to the simulator from the top-level README
Hopefully this will help a little with awareness of the existence of the
simulator.
@@ -25,6 +25,7 @@ Instructions for different operating systems can be found here:
- [Zephyr](docs/readme-zephyr.md)
- [Mynewt](docs/readme-mynewt.md)
- [RIOT](docs/readme-riot.md)
+- [Simulator](sim/README.rst)
## Roadmap
