Add clone to builder state types

[JunichiSugiura]

This PR is to add Clone impl to both DefaultState and AsyncState. This allows ConfigBuilder to be fully clonable. My goal is to make bevy plugin that inserts ConfigBuilder as resource so that developers can query them from systems and modify (e.g. configure additional source file etc.).

I'm not 100% sure this is a right approach but it satisfied my use case for now. Let me know if there's other way to make it work.

Example

• PoC PR
• code

Without clone

🦄  cargo run --example cli_config
   Compiling dip v0.1.0 (/Users/js/projects/github.com/JunichiSugiura/dip)
error[E0507]: cannot move out of dereference of `dip::prelude::ResMut<'_, ConfigBuilder<DefaultState>>`
  --> examples/cli/config/main.rs:17:16
   |
17 |     *builder = builder.add_source(File::with_name("examples/cli/config/config/development"));
   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ move occurs because value has type `ConfigBuilder<DefaultState>`, which does not implement the `Copy` trait

[matthiasbeyer]

I don't see why the states couldn't be Clone, so yes, I think we can merge this (if CI is green of course 😆 ).

[JunichiSugiura]

What's the status on this PR?

[matthiasbeyer]

Ah, thanks for pinging me!

[JunichiSugiura]

Thanks for the merge !

[JunichiSugiura]

@matthiasbeyer Hi, what's the plan for publishing a new version including this PR? This has been a blocker to bump my lib.

[matthiasbeyer]

Hm. Can this be considered a backwards compatible fix? I am not sure. If it is, I could release a patchlevel version update.

[JunichiSugiura]

@matthiasbeyer This PR just adds Clone trait so the old code still works without any changes, I think.

[matthiasbeyer]

Submitted backport in #398

Will release 0.13.3 with this patch shortly.

[JunichiSugiura]

@matthiasbeyer Thank you so much 🙏