Relicense bevy_atmosphere under dual MIT/Apache-2.0

[JonahPlusPlus]

When I started this, I didn't know too much about dual licensing, or its benefits. In order to keep this project in line with the Bevy project, I would like to "relicense" this project under the same licenses. I'm going to follow the same path for relicensing as Bevy (see here) and ask every contributor (as of this message and minus the bot) to give their consent by leaving the following comment:

I license past and future contributions under the dual MIT/Apache-2.0 license, allowing licensees to choose either at their option.

Once I get consent from everyone involved, I'll merge this PR. Hopefully, it'll be done by the time I'm finished with the 0.4 release.

Contributor Check-off

• @JonahPlusPlus
• @Shatur
• @cryscan
• @Aceeri
• @kbieganski

[JonahPlusPlus]

I license past and future contributions under the dual MIT/Apache-2.0 license, allowing licensees to choose either at their option.

[kbieganski]

I license past and future contributions under the dual MIT/Apache-2.0 license, allowing licensees to choose either at their option.

[Aceeri]

I license past and future contributions under the dual MIT/Apache-2.0 license, allowing licensees to choose either at their option.

[Shatur]

I license past and future contributions under the dual MIT/Apache-2.0 license, allowing licensees to choose either at their option.

[JonahPlusPlus]

@cryscan I would really like to get your input on this. While your changes have been overwritten in this last update, I would still like to get your consent if possible, just to make sure everyone is on the same page and that there won't be any future issues surrounding this.

[cryscan]

I license past and future contributions under the dual MIT/Apache-2.0 license, allowing licensees to choose either at their option.

[JonahPlusPlus]

Thank you everyone for your contributions. I'll be having this update out in a couple days, just need to rewrite documentation. The current main branch is now up to date, so if you would like to test it out, any feedback is appreciated.