Implemented the KeyNameFilter filter and conformed it to the Filter protocol.

Sources/Filters/KeyNameFilter.swift

@@ -0,0 +1,56 @@
+public struct KeyNameFilter {
+    
+    // MARK: Properties
+    
+    private let key: String?
+    private let name: String?
+    
+    // MARK: Initialisers
+    
+    public init(
+        key: String?,
+        name: String?
+    ) {
+        self.key = key
+        self.name = name
+    }
+
+}
+
+// MARK: - Filter
+
+extension KeyNameFilter: Filter {
+    
+    // MARK: Functions
+    
+    func makeParameters() -> [String : String?] {
+        var parameters: [String : String?] = [:]
+        
+        if let key {
+            parameters[.Key.key] = key
+        }
+        
+        if let name {
+            parameters[.Key.name] = name
+        }
+        
+        return parameters
+    }
+    
+}
+
+// MARK: - Type aliases
+
+public typealias AmiiboSeriesFilter = KeyNameFilter
+public typealias AmiiboTypeFilter = KeyNameFilter
+public typealias CharacterFilter = KeyNameFilter
+public typealias GameSeriesFilter = KeyNameFilter
+
+// MARK: - String+Key
+
+private extension String {
+    enum Key {
+        static let key = "key"
+        static let name = "name"
+    }
+}