Use ILRepack to include Microsoft.OpenApi as internal (#1290)

* .

* Use ILRepack to include Microsoft.OpenApi as internal

* ...

* OpenApiSpecificationVersion

* .

* 080

* 4

src-old/WireMock.Net.OpenApiParser/Extensions/DictionaryExtensions.cs

@@ -0,0 +1,22 @@
+// Copyright © WireMock.Net
+
+#if NET46 || NETSTANDARD2_0
+using System.Collections.Generic;
+
+namespace WireMock.Net.OpenApiParser.Extensions;
+
+internal static class DictionaryExtensions
+{
+    public static bool TryAdd<TKey, TValue>(this Dictionary<TKey, TValue>? dictionary, TKey key, TValue value)
+    {
+        if (dictionary is null || dictionary.ContainsKey(key))
+        {
+            return false;
+        }
+
+        dictionary[key] = value;
+
+        return true;
+    }
+}
+#endif