Add: detailed doc for OpCode

Author: Wi1l-B0t

src/Neo.VM/JumpTable/JumpTable.Control.cs

@@ -635,7 +635,7 @@ public virtual void ExecuteJumpOffset(ExecutionEngine engine, int offset)
     public virtual void ExecuteTry(ExecutionEngine engine, int catchOffset, int finallyOffset)
     {
         if (catchOffset == 0 && finallyOffset == 0)
-            throw new InvalidOperationException($"catchOffset and finallyOffset can't be 0 in a TRY block");
+            throw new InvalidOperationException($"catchOffset and finallyOffset can't both be 0 in a TRY block.");
         if (engine.CurrentContext!.TryStack is null)
             engine.CurrentContext.TryStack = new Stack<ExceptionHandlingContext>();
         else if (engine.CurrentContext.TryStack.Count >= engine.Limits.MaxTryNestingDepth)

src/Neo.VM/JumpTable/JumpTable.Splice.cs

@@ -63,6 +63,7 @@ public virtual void Memcpy(ExecutionEngine engine, Instruction instruction)
 
     /// <summary>
     /// Concatenates two buffers and pushes the result onto the evaluation stack.
+    /// The result is the first pushed item concatenated with the second pushed item.
     /// <see cref="OpCode.CAT"/>
     /// </summary>
     /// <param name="engine">The execution engine.</param>
@@ -82,7 +83,7 @@ public virtual void Cat(ExecutionEngine engine, Instruction instruction)
     }
 
     /// <summary>
-    /// Extracts a substring from the specified buffer and pushes it onto the evaluation stack.
+    /// Extracts a sub-buffer from the specified buffer and pushes it onto the evaluation stack.
     /// <see cref="OpCode.SUBSTR"/>
     /// </summary>
     /// <param name="engine">The execution engine.</param>