Better title for functors.md

Co-authored-by: Michael Abbott <[email protected]>

Author: Saransh-cpp

docs/src/models/functors.md

@@ -1,6 +1,6 @@
-# Functor from Functors.jl
+# Recursive transformations from Functors.jl
 
-Flux makes use of the [Functors.jl](https://github.com/FluxML/Functors.jl) to represent many of the core functionalities it provides.
+Flux models are deeply nested structures, and [Functors.jl](https://github.com/FluxML/Functors.jl) provides tools needed to explore such objects, apply functions to the parameters they contain, and re-build them.
 
 Functors.jl is a collection of tools designed to represent a [functor](https://en.wikipedia.org/wiki/Functor_(functional_programming)). Flux makes use of it to treat certain structs as functors. Notable examples include the layers that Flux defines.