Improve toggle configuration experience

[Noorts]

As requested by a review on the JetBrains marketplace.

The current approach of managing the dictionary within the small settings window is suboptimal. I would prefer the ability to edit a JSON file directly within Rider for a more efficient process.

Being able to edit the configuration in the IDE's editor would be great indeed (with all the editing features developers are used to).

I've looked into the feasibility of this before briefly and it seemed non trivial. It would be nice to either:

1. Completely replace the current limited configuration window, keeping only the buttons that are there right now and adding a "Configure in Editor" button. Clicking the button will open the toggles configuration file in the IDE's editor. Making changes and saving the file will apply the changes.
   • There would have to be some kind of validation to make sure the toggles are unique, and to make sure the file contains an "array and string only" subset of JSON. It might be possible to use this plugin's already existing validation logic.
   • Note: This approach is similar to the one taken by HiDeoo's Toggler extension for VSCode.
2. Bring the editor capabilities into the current configuration window.

I personally prefer approach 1.

Note that I'd like to make sure that Toggler users do not lose their current toggles when they update to a new version that includes this functionality.