Rollup merge of #33893 - Ophirr33:docs_string_split_fix, r=GuillaumeGomez

Added examples/docs to split in str.rs

Added documentation clarifying the behavior of split when used with the empty string and contiguous separators. Addresses issue [33882](https://github.com/rust-lang/rust/issues/33882). This is my first time contributing to rust, so forgive me if I'm skipping any of the contribution steps.
Fixes #33882