Update configure logic to support tsdown

[samchungy]

skuba/src/cli/configure/modules/package.ts

Lines 7 to 12 in ddde63a

	const DEFAULT_PACKAGE_FILES = [
	'lib*/**/*.d.ts',
	'lib*/**/*.js',
	'lib*/**/*.js.map',
	'lib*/**/*.json',
	];

Needs to be updated to write a tsdown.config.mts file and update the entrypoints + files

[samchungy]

Bit of a thought dump on what to do:

Replace files with ['lib'].

Maybe can read the existing template tsdown.config.mts https://github.com/seek-oss/skuba/blob/main/template/private-npm-package/tsdown.config.mts.

Will need to replace the custom condition within the tsdown.config.mts.

Need to remove the main/types/module override and just do a dry-run of skuba build-package so tsdown can override them for us.