Auto merge of #79641 - sourcefrog:split-example, r=dtolnay
Auto merge of #79641 - sourcefrog:split-example, r=dtolnay

Add a doctest example of str::split on a slice of chars

This is mentioned as supported, but the semantics are not described.

graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust