add flag to multiple-cursors module that uses iedit package

### Describe your request

The [iedit](https://github.com/victorhge/iedit) package is a simple and robust multiple-cursors option that would be great to include as an option in the multiple-cursors module. It may not have as many features as the other packages, but it is very fast, very reliable, and handles most "normal" use cases that people might encounter.

### Briefly explain its use-case

Add an `+iedit` flag to the multiple-cursors module which uses the iedit package instead of other alternatives. After it is enabled, then the default keybinding could (should?) be set up (the default is `C-;`) to toggle the mode on/off. This keybinding can be overridden in config.el.

Start by reading the multiple-cursors module and how its existing package flags and keybindings are defined; inspect iedit's interface and the current config.el override behavior. Add an +iedit option that uses iedit and supports the proposed C-; toggle, then verify the module loads and the binding can be overridden in config.el.

Written by the indexing model from the issue text.