docs: Update collections README with HashMap link

lauralindzey · web-flow · commit 8774e47dc34c · 2021-07-06T01:31:27.000-07:00
diff --git a/exercises/collections/README.md b/exercises/collections/README.md
@@ -20,3 +20,4 @@ structures that are used very often in Rust programs:
 ## Further information
 
 - [Storing Lists of Values with Vectors](https://doc.rust-lang.org/stable/book/ch08-01-vectors.html)
+- [Storing Keys with Associated Values in Hash Maps](https://doc.rust-lang.org/book/ch08-03-hash-maps.html)

Original file line number	Diff line number	Diff line change
`@@ -20,3 +20,4 @@ structures that are used very often in Rust programs:`
`20`	`20`	`## Further information`
`21`	`21`
`22`	`22`	`- [Storing Lists of Values with Vectors](https://doc.rust-lang.org/stable/book/ch08-01-vectors.html)`
	`23`	`+- [Storing Keys with Associated Values in Hash Maps](https://doc.rust-lang.org/book/ch08-03-hash-maps.html)`