[RFC]: add support for persisting REPL configuration across sessions

### Description

This RFC proposes adding support for REPL configuration files to persist user preferences (eg. settings) across each session.

### Questions

- What to persist? For starters, we can persist settings, themes, and most of the options that the REPL receives during instantiation like `inputPrompt`, `welcomeMessage`, `padding` etc. I think we should avoid saving options like `load` and others which are something that is typically used per session.

- If we end up NOT saving anything else than what already can be passed as REPL options, does it make sense to have commands for loading custom configuration files? As loading a configuration or just loading the REPL options is pretty much the same process. In that case, just having a single configuration that *remembers* user preferences is more than enough, as the user can have scripts with specific options for different use-cases/profiles.

### Other

Saving command history is an existing *TODO*, once we support that maybe we can also auto-persist them. I believe IPython does this.

### Checklist

- [X] I have read and understood the [Code of Conduct](https://github.com/stdlib-js/stdlib/blob/develop/CODE_OF_CONDUCT.md).
- [X] Searched for existing issues and pull requests.
- [X] The issue name begins with `RFC:`.

Start by mapping the REPL entry point and the options it receives, then review the existing command-history TODO referenced in the RFC. Resolve which settings, themes, and instantiation options should persist while excluding per-session options such as `load`; done means an agreed configuration format and persistence behavior.

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