Add docs for how to install

Author: saulshanabrook

docs/index.md

@@ -3,6 +3,10 @@
 `egg-smol` is a Python package that provides bindings to the Rust library `egg-smol`,
 allowing you to use e-graphs in Python for optimization, symbolic computation, and analysis.
 
+```shell
+pip install egg-smol
+```
+
 ```{toctree}
 tutorials
 how-to-guides