Note in README

README.md

@@ -5,6 +5,12 @@ Unfold values on-demand from a function.
 [![Package Version](https://img.shields.io/hexpm/v/gleam_yielder)](https://hex.pm/packages/gleam_yielder)
 [![Hex Docs](https://img.shields.io/badge/hex-docs-ffaff3)](https://hexdocs.pm/gleam_yielder/)
 
+
+You may want to use this library when you have a function that can generate a
+sequence of values but the sequence is too large to fit into memory, or it would
+be wasteful to do so. You could instead create a `Yielder` for it and only have
+the section you are working on in memory, and halt evaluation when you have
+consumed as much of the sequence as you need for your program.
 ```sh
 gleam add gleam_yielder@1
 ```