bug/issue 1346 bundle transitive CSS url(...) references

[thescientist13]

Related Issue

resolves #1346

Should now see a lot less Unable to resolve ... messages, as per AnalogStudiosRI/www.analogstudios.net#101

Documentation

1. Will want to make sure any of these node_modules resolutions carry over to the CSS side as well - improve documentation around referencing scripts, styles, and import map diagnostics www.greenwoodjs.dev#144

Summary of Changes

1. Leverage workingUrl to better handling bundling of relative url(...) references in CSS files
2. Add test cases

TODO

1. Are we properly handling all explicit case of ./. ../, and / (where / is not a reference to node_modules)