[Feature]: Support import asset in bundleless mode

[Timeless0911]

What problem does this feature solve?

We only deals js externsion in externals when in bundleless mode.

rslib/packages/core/src/config.ts

Lines 667 to 689 in 057cd87

	externals: [
	(data: any, callback: any) => {
	// Issuer is not empty string when the module is imported by another module.
	// Prevent from externalizing entry modules here.
	if (data.contextInfo.issuer) {
	// Node.js ECMAScript module loader does no extension searching.
	// Add a file extension according to autoExtension config
	// when data.request is a relative path and do not have an extension.
	// If data.request already have an extension, we replace it with new extension
	// This may result in a change in semantics,
	// user should use copy to keep origin file or use another separate entry to deal this
	let request = data.request;
	if (request[0] === '.') {
	request = extname(request)
	? request.replace(/\.[^.]+$/, jsExtension)
	: `${request}${jsExtension}`;
	}
	return callback(null, request);
	}
	callback();
	},
	],

What does the proposed API look like?

• assets can be externalize
• assets have correct redirect path [Feature]: Redirect in bundleless mode #140