Change ESM builds for R3F extension so the components are treeshakeable 🌲

[juniorxsound]

What?

Right now when esbuilding the R3F extension everything is bundled into a single file for both ESM and CJS builds (including import statements to @theatre/studio which are only required by some of the components). This PR moves to building an ESM version without bundling all components to a single file, that way separate components can be imported by the user without fear that studio would be included in your bundle when not needed (e.g when importing just editable without studio in the project).

Before

Here is a snapshot of the current build output (esm target builds a single index.mjs file with everything inlined)

After

Each component is built into JS but kept separated by turning `esbuild`'s `bundle` prop off - that way components can be imported individually without having to import the whole `index.mjs` dependencies.

Closes #97

[nbartzokas]

LGTM!

[AriaMinaei]

Thanks for the PR @juniorxsound and @nbartzokas!

@AndrewPrifer is fixing up the build system via #101 so I think this PR would be reviewed as part of that task.

[AndrewPrifer]

This is now (finally, yay) addressed by #129, along with various other issues. Thanks for your contribution @juniorxsound, we ended up using your solution and even removing the cjs build altogether.