Add an example to README

README.md

@@ -14,6 +14,25 @@ Get the latest stable release with Julia's package manager:
 ] add CoordGridTransforms
 ```
 
+## Usage
+
+To use the conversions defined in CoordGridTransforms.jl, 
+use it together with CoordRefSystems.jl in the same environment:
+
+```julia
+julia> using CoordRefSystems, CoordGridTransforms
+
+julia> c = LatLon{SAD96}(-15, -45)
+GeodeticLatLon{SAD96} coordinates
+├─ lat: -15.0°
+└─ lon: -45.0°
+
+julia> convert(LatLon{SIRGAS2000}, c)
+GeodeticLatLon{SIRGAS2000} coordinates
+├─ lat: -15.000451566492272°
+└─ lon: -45.00042666174454°
+```
+
 [build-img]: https://img.shields.io/github/actions/workflow/status/JuliaEarth/CoordGridTransforms.jl/CI.yml?branch=main&style=flat-square
 [build-url]: https://github.com/JuliaEarth/CoordGridTransforms.jl/actions