docs: Add documentation comments

Sources/Hiero/Transaction/TransactionHash.swift

@@ -2,13 +2,17 @@
 
 import Foundation
 
+/// The SHA-384 hash of a transaction, used to uniquely identify transactions on the network.
 public struct TransactionHash: CustomStringConvertible {
+    /// Creates a transaction hash by computing SHA-384 of the given data.
     internal init(hashing data: Data) {
         self.data = Sha2.sha384(data)
     }
 
+    /// The raw bytes of the SHA-384 hash.
     public let data: Data
 
+    /// Returns the hash as a hex-encoded string.
     public var description: String {
         data.hexStringEncoded()
     }