Add Text Attachments Delegate

### Description Adds an API for receiving events from the text attachments manager. ### Related Issues N/A ### 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 N/A