Mention MathOptFormat.jl

Author: odow

README.md

@@ -165,3 +165,10 @@ required keys at the top level:
 
 A number of examples of optimization problems encoded using MathOptFormat are
 provided in the [`/examples` directory](https://github.com/odow/MathOptFormat/tree/master/examples).
+
+## Implementations
+
+- Julia
+
+  - The [MathOptFormat.jl](https://github.com/odow/MathOptFormat.jl) package
+    supports reading and writing MathOptFormat files.