Prefer `forge.config.js` syntax over `package.json` configuration

[erickzhao]

Pre-flight checklist

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project uses.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Problem description

After some recent discussion, the maintainers have decided to prefer forge.config.js syntax over the package.json configuration field.

Proposed solution

I think there are a few things to improve here:

• Update Configuration docs in accordance.
• Update other docs to feature JS syntax rather than JSON.
• Update import and init commands to generate a forge.config.js file.

Alternatives considered

N/A

Additional information

No response