Update readme to have info about performance test dashboard

Author: tdrwenski

README.md

@@ -130,7 +130,12 @@ Regression tests are defined in `tests/regression` and can be run with
 ```
 pytest tests/regression
 ```
-See tests/regression/README.md for more information.
+See `tests/regression/README.md` for more information.
+
+## Performance tests
+Performance regression tests are defined in `tests/performance`.
+The latest results from `main` are shown on this [performance dashboard](https://software.llnl.gov/quandary/dev/bench/).
+See `tests/performance/README.md` for more information.
 
 # Community and Contributing