Documentation missing mandatory metadata

[ajchili]

Describe the bug

When running npx jsii-config, main is a mandatory field for my package.json file.

Expected Behavior

I would expect the documentation to state this as a required field.

Current Behavior

Process fails and I have added main to my package.json file.

Reproduction Steps

1. Create a package
2. Exclude the main field from the package.json file
3. Run npx jsii-config

Possible Solution

Update the author set-up guide to specify that main is a required field.

Additional Information/Context

No response

SDK version used

Not sure, failed before jsii was configured.

Environment details (OS name and version, etc.)

MacOS 12.2 + Node.JS 14.18.3 + NPM 6.14.15

[ajchili]

Perhaps there can be two author guides, one for new packages and one for existing packages?

[mrgrain]

Related to #4259