Add Bevy 0.12 support

[w512]

It seems that the current version of the library is not compatible with the latest version of Bevy (0.12).

the trait bevy_app::plugin::sealed::Plugins<_> is not implemented for (VertexPullingRenderPlugin,)

[MarijnS95]

Note that this upgrade was performed in #25, and the 0.13 upgrade is being done in #27.