CHANGELOG updated

docs/CHANGELOG.md

@@ -6,6 +6,7 @@
   - Added angle as SI base dimension (thanks [@kwikius](https://github.com/kwikius))
   - Added STL random number distribution wrappers (thanks [@yasamoka](https://github.com/yasamoka))
   - `math.h` function signatures refactored to use a `Quantity` concept (thanks [@kwikius](https://github.com/kwikius))
+  - FPS system added (thanks [@mikeford3](https://github.com/mikeford3))
 
 - **0.5.0 May 17, 2020**
   - Major refactoring and rewrite of the library