Implements verifier and code gen for swift (#6373)

Updates test cases on linux

Adhere to new protocol naming

Adds fuzzing

Adds documentation

Adds support for string unions

Updated fuzzer generated code

swift/Sources/FlatBuffers/Struct.swift

@@ -16,16 +16,30 @@
 
 import Foundation
 
+/// Struct is a representation of a mutable `Flatbuffers` struct
+/// since native structs are value types and cant be mutated
 @frozen
 public struct Struct {
+
+  /// Hosting Bytebuffer
   public private(set) var bb: ByteBuffer
+  /// Current position of the struct
   public private(set) var postion: Int32
 
+  /// Initializer for a mutable flatbuffers struct
+  /// - Parameters:
+  ///   - bb: Current hosting Bytebuffer
+  ///   - position: Current position for the struct in the ByteBuffer
   public init(bb: ByteBuffer, position: Int32 = 0) {
     self.bb = bb
     postion = position
   }
 
+  /// Reads data from the buffer directly at offset O
+  /// - Parameters:
+  ///   - type: Type of data to be read
+  ///   - o: Current offset of the data
+  /// - Returns: Data of Type T that conforms to type Scalar
   public func readBuffer<T: Scalar>(of type: T.Type, at o: Int32) -> T {
     let r = bb.read(def: T.self, position: Int(o + postion))
     return r