Feature Request: Dump/persist editor state to disk (extension?)

One feature of `nano` I use to massively accelerate my workflows is its `filepos_history` file. That file simply contains a MRU list of file paths and their last cursor position. `nano` itself obviously uses this to remember your cursor position in files between `nano` launches--which is great!--but I also use this list in shell scripts and workflows to great effect and I couldn't live without these. They are nearly mandatory for someone who doesn't live in their editor but instead live in their shell, which is a use-case very befitting of `edit` and which you should consider supporting.

`nano` also persists search queries in `search_history`, allowing to simply up- and down-arrow in the find dialog like at the shell prompt between `nano` launches. Very, very handy.

My workflows depend so much on rapidly and usefully entering and exiting my editor that I'm finding myself wanting to write my own just so I can make it dump/persist its text selection and undo history, too (which `nano` doesn't do).

My request is for the capability of dumping the editor state to disk in a trivially readable and editable format fit for integration with other tools and scripts. In trying to suggest this in the most appropriate way and looking at #17 I think that this feature should be suggested as an extension? By editor state I have in mind:

- Opened file path
- Cursor position
- Scroll offset
- Selections (relevant: #24)
- Search/replace history
- Undo history

This feature has very high synergy with #89 and together they present a highly _integrating_ view of program extension which gels really well with composition of **small tools** (as opposed to giant monolithic tools like VSCode, Visual Studio, etc).

No files, tests, or entry points are named. Start by reviewing the extension discussion in #17 and the related selection and integration work in #24 and #89; done would require an agreed, readable on-disk format covering the requested editor state.

Written by the indexing model from the issue text.