Add documentation explaining BoolContainer and StringNumberContainer purpose

Author: VladislavFitz

Sources/AlgoliaSearchClient/Helpers/Coding/Wrappers/BoolContainer.swift

@@ -7,6 +7,10 @@
 
 import Foundation
 
+/**
+ Helper structure ensuring the decoding of a bool value from a "volatile" JSON
+ occasionally providing bool values in the form of String   
+ */
 struct BoolContainer: RawRepresentable, Codable {
 
   let rawValue: Bool

Sources/AlgoliaSearchClient/Helpers/Coding/Wrappers/StringNumberContainer.swift

@@ -7,6 +7,10 @@
 
 import Foundation
 
+/**
+  Helper structure ensuring the decoding of a number value from a "volatile" JSON
+  occasionally providing number values in the form of String
+*/
 struct StringNumberContainer: RawRepresentable, Codable {
 
   let rawValue: Double