fix locale and dojo/i18n issues on node, fixes #16663

- avoid exception in dojo/_base/config when navigator isn't defined
- make dojo/i18n handle case when dojo.locale is undefined
Add README.md and CONTRIBUTING.md, refs #17189
add missing quotes, fixes #17199
Fixes relative paths when using dojo/node, fixes #16414
Only require selector/_loader when DOM present. Fixes #17138.
Fix typo in CONTRIBUTING.md, refs #17189. Thanks @Maastermedia.