Select Undone/Redone Text

### Description Updates the undo manager to update the text selection when undoing/redoing. Two cases: - Replaced/Inserted text - selects the inserted text - Deleted text - Places cursor at the start of the deleted text, as if the user had just deleted it. ### Related Issues * closes #95 ### Checklist - [x] I read and understood the [contributing guide](https://github.com/CodeEditApp/CodeEdit/blob/main/CONTRIBUTING.md) as well as the [code of conduct](https://github.com/CodeEditApp/CodeEdit/blob/main/CODE_OF_CONDUCT.md) - [x] The issues this PR addresses are related to each other - [x] My changes generate no new warnings - [x] My code builds and runs on my machine - [x] My changes are all related to the related issue above - [x] I documented my code ### Screenshots https://github.com/user-attachments/assets/55309316-9106-4ce2-ac25-952e2addbbfe