Integrated Analytics into the Infrastructure package (#40)

This PR contains the work done to define the `Analytics` type into the _Infrastructure_ package and also, to integrate this type into its `Page` protocol.

Reviewed-on: rock-n-code/loud-amsterdam#40
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>

Packages/Infrastructure/Tests/Utils/Pages/StubPage.swift

@@ -7,6 +7,9 @@ struct StubPage: Page {
 
     // MARK: Properties
 
+    /// The analytics tracker rendered as a deferred script in the document head, or `nil` to omit it.
+    let analytics: Analytics?
+
     /// The version token appended to the page's asset URLs, or `nil` to leave them unversioned.
     let assetVersion: String?
 
@@ -34,6 +37,8 @@ struct StubPage: Page {
     ///     default) to leave them unversioned.
     ///   - canonicalURL: the canonical URL rendered in the document head, or `nil` (the default)
     ///     to omit it.
+    ///   - analytics: the analytics tracker rendered as a deferred script in the document head,
+    ///     or `nil` (the default) to omit it.
     ///   - socialCard: the card rendered as link-preview tags in the document head, or `nil`
     ///     (the default) to omit them.
     ///   - structuredData: the structured data rendered as a JSON-LD script in the document
@@ -44,10 +49,12 @@ struct StubPage: Page {
         locale: Locale = .init(identifier: "en"),
         assetVersion: String? = nil,
         canonicalURL: String? = nil,
+        analytics: Analytics? = nil,
         socialCard: SocialCard? = nil,
         structuredData: StructuredData? = nil,
         summary: String? = nil
     ) {
+        self.analytics = analytics
         self.assetVersion = assetVersion
         self.canonicalURL = canonicalURL
         self.locale = locale