### What it does
Suggests using `strip_{prefix,suffix}` over `str::{starts,ends}_with` and slicing using
the pattern's length.

### Why is this bad?
Using `str:strip_{prefix,suffix}` is safer and may have better performance as there is no
slicing which may panic and the compiler does not need to insert this panic code. It is
also sometimes more readable as it removes the need for duplicating or storing the pattern
used by `str::{starts,ends}_with` and in the slicing.

### Example
```
let s = "hello, world!";
if s.starts_with("hello, ") {
    assert_eq!(s["hello, ".len()..].to_uppercase(), "WORLD!");
}
```
Use instead:
```
let s = "hello, world!";
if let Some(end) = s.strip_prefix("hello, ") {
    assert_eq!(end.to_uppercase(), "WORLD!");
}
```