cookie.Manager and DefaultManager (#8)


* `cookie.Manager` is now the primary API to the package
* `cookie.DefaultManager` is initialized and provides API stability for the global `Set/Get/...` methods.
* `Options` API Change:
  * `cookie.NewManager(cookie.WithSigningKey(signingKey))`
* Introduction of `CustomTypeHandler` so we no longer impose a specific dependency (gofrs/uuid)
* Significant upgrade to the `PopulateFromCookies` functionality
* File organization for better separation of functionality and tests
* Removal of `DefaultOptions` - The `mergeOptions` functionality wasn't working well anyways.
* Adds `omitempty` to silently ignore missing cookies.

Package Cleanup (#7)

* cleaning up errors so they are errors.Is able

* assert error types

* correct name for test

* showcase default options in example

* unsigned up top

* update documentaiton lines to be specific

minor restructuring and removing unused error

Merge pull request #3 from syntaqx/test-coverage

100% Test Coverage

return ErrNoCookie to ensure that errors arent hidden

use http.MethodGet

Merge branch 'main' of github.com:syntaqx/cookie

update docs