Add settings docs

[BrainMaestro]

Finish last part of #230. Does this need to be more detailed?

[KELiON]

Thanks for adding it!

[KELiON]

1. There is also label option to specify label text (it is just a field name by default)
2. I'd notice that options and multi applicable only for array and option types
3. For array and option types also could be added clearable and creatable options
4. We can add screenshot to show how plugin settings look like
5. We can add a link to react-select configuration to clarify what is creatable, multi, and clearable. Also, to clarify format of options object
6. And the latest step is to add an example plugin with settings to examples.md

[BrainMaestro]

1. True
2. multi should actually only be applicable to option. array probably shouldn't ever be restricted to just one value.
3. The idea for array was to be the creatable version of option. I think they should all just be clearable by default, but that can be added.

I'll update the others

[KELiON]

@BrainMaestro agree with 2, but not with 3. I think it is possible case to select the list of provided options, without ability to add new ones, but at the same time it is possible to choose only one, but with ability to create it by user. What do you think?

[BrainMaestro]

Okay I think that's fine

[BrainMaestro]

I think we no longer need the array type though. Since option can allow the user to create their own option. It should just handle all the possible scenarios.
What do you think?

[KELiON]

@BrainMaestro makes sense! because type=option + multi will be the same as type=array. Let's just leave one

[BrainMaestro]

I updated this with an example and removed the array type. I can make a separate PR to remove the array type from the codebase.

[KELiON]

👏👏👏