Adjustments to the Localization package dependency (#11)

This PR contains the work done to refactor the _Localization_ package and tidy the project a little bit.

To provider further details about the work:

* The `Negotiate` function was moved to the _Localization_ package.
* The `WebsiteRequestContext` context no longer resolves a default language at creation; it starts empty and relies on the `LocalizationMiddleware` middleware to fill it in.
* Fixed the local dependency path to Packages/Localization for the **Website** package as it only resolved inside the Xcode workspace before, breaking swift build, the Makefile, and the Docker build).
* Updated the `README` file to document language negotiation, the GET /health route, and the full middleware chain; doc comments across the moved/renamed types were brought back in sync with the code.

Reviewed-on: rock-n-code/loud-amsterdam#11
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Services/Website/Sources/Library/Public/Contexts/LocalizedRequestContext.swift

@@ -1,5 +1,4 @@
 import Hummingbird
-import Localization
 
 /// A request context that carries the language negotiated for the request.
 ///
@@ -34,9 +33,17 @@ public struct WebsiteRequestContext: LocalizedRequestContext {
 
     /// Creates a request context for the given source.
     /// - Parameter source: the source the context is initialized from.
-    public init(source: Source) {
+    public init(
+        source: Source,
+    ) {
         self.coreContext = .init(source: source)
-        self.language = LanguageList(bundle: .module).default
+        self.language = .empty
     }
 
 }
+
+// MARK: - Constants
+
+private extension String {
+    static let empty = ""
+}