Pull out Manganis CLI support into a separate crate

[ealmloff]

Refactor Request

The code to support manganis assets and asset optimization currently lives in the CLI (introduced in #3195). This means we don't need a stable API and it is fairly easy to integrate, but it makes it difficult to use manganis from other CLIs and it adds a lot of required dependencies to the CLI

It would be nice to pull out the optimization into a separate crate to make the CLI easier to maintain and could make it easier to move manganis optimization under a feature flag

[jkelleyrtp]

Oh forgot I did this - #3273

It's named specific to dioxus but could/should be renamed to something manganis-specific.