Implementation of the Line Breaking Algorithm described in Unicode Standard Annex #14.
Given an input text, locates "line break opportunities", or positions appropriate for wrapping lines when displaying text.
```rust use unicode_linebreak::{linebreaks, BreakOpportunity::{Mandatory, Allowed}};
let text = "a b \nc"; assert!(linebreaks(text).eq(vec![ (2, Allowed), // May break after first space (5, Mandatory), // Must break after line feed (6, Mandatory) // Must break at end of text, so that there always is at least one LB ])); ```