Merge #325

325: implement translate_offset_with_edit r=matklad a=vemoo

- Implement `translate_offset_with_edit` to resolve #105 
- Add proptest impls for text, offsets and edits and use them in tests for `translate_offset_with_edit` and `LineIndex`
- Added benchmark for `translate_offset_with_edit`

Co-authored-by: Bernardo <berublan@gmail.com>

crates/ra_editor/src/lib.rs

@@ -2,6 +2,7 @@ mod code_actions;
 mod extend_selection;
 mod folding_ranges;
 mod line_index;
+mod line_index_utils;
 mod symbols;
 #[cfg(test)]
 mod test_utils;
@@ -12,6 +13,7 @@ pub use self::{
     extend_selection::extend_selection,
     folding_ranges::{folding_ranges, Fold, FoldKind},
     line_index::{LineCol, LineIndex},
+    line_index_utils::translate_offset_with_edit,
     symbols::{file_structure, file_symbols, FileSymbol, StructureNode},
     typing::{join_lines, on_enter, on_eq_typed},
 };