Rollup merge of #135381 - cod10129:vec-splice-doc, r=tgross35

Add an example for `Vec::splice` inserting elements without removing

This example clearly showcases how `splice` can be used to insert multiple elements efficiently at an index into a vector.

Fixes #135369.

The added example:

> Using `splice` to insert new items into a vector efficiently at a specific position indicated by an empty range:
> ```rust
> let mut v = vec![1, 5];
> let new = [2, 3, 4];
> v.splice(1..1, new);
> assert_eq!(v, [1, 2, 3, 4, 5]);
> ```

`@rustbot` label A-docs A-collections

0 files changed, 0 insertions, 0 deletions