feat: migrate to http and ky-universal

[pi0]

• [x] Use ky dependency
• [x] Header helpers: setHeader / setToken (Scope support removed)
• [x] Hooks: onRequest/onResponse/onRequestError/onResponseError/onError
• [x] $ helpers
• [x] Debug Users can create their own debugger
• [x] Retry (KY has built-in support - default changed to 0)
• [x] Auto credentials setter (Removed as KY uses same-origin header by default)
• [x] Progress (Removed due to lack of fetch support)
• [x] Support JSON body as second arg (Not possible. Users have to use { json: {} })
• [x] Update readme
• [x] Update tests
• [x] Update docs

TODO

• [ ] Headers is not a constructor for tests
• [x] Global retry and docs
• [x] Types
• [x] Basic Migration Guide