🏭 Add BasicAuth addon

[BendingBender]

Implement BasicAuth addon that adds following behaviors:

• allows setting credentials via the .basicAuth() method
• parses URLs and extracts credentials from them, converting them to an Authorization header and removing them from the URL which would otherwise throw an error when passed to native fetch()
• correctly encodes usernames/passwords that contain non-latin characters (see https://developer.mozilla.org/en-US/docs/Glossary/Base64#the_unicode_problem)

Fixes #221

[BendingBender]

I have a question here: I also use the encodeURIComponent and btoa globals in my addon. Should I inject them via the polyfill system, just like URL and TextEncoder or do you think that this is the absolute baseline that doesn't need polyfilling?

[ChiliBoyRed]

I have a question here: I also use the encodeURIComponent and btoa globals in my addon. Should I inject them via the polyfill system, just like URL and TextEncoder or do you think that this is the absolute baseline that doesn't need polyfilling?

If you intend to make this compatible with React Native, it doesn't support atob or btoa (yet) other than through polyfills.

[BendingBender]

I have a question here: I also use the encodeURIComponent and btoa globals in my addon. Should I inject them via the polyfill system, just like URL and TextEncoder or do you think that this is the absolute baseline that doesn't need polyfilling?

If you intend to make this compatible with React Native, it doesn't support atob or btoa (yet) other than through polyfills.

This should already work in any environment that has native btoa or has it already polyfilled globally. So the question is actually whether we need to support local polyfills (i.e. only for this lib). I don't use RN and have no experience with it. Can you tell me whether it's common to globally polyfill btoa there?