Add AssemblyMetadataAttribute for NET35 and NET40

Author: austinv900

src/Oxide.Common.csproj

@@ -11,7 +11,7 @@
     <PackageIconUrl>icon.png</PackageIconUrl>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageProjectUrl>$(RepositoryUrl)</PackageProjectUrl>
-    <TargetFrameworks>net35;net48;netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net35;net40;net45;net46;net48;netstandard2.0;netstandard2.1</TargetFrameworks>
     <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
     <NoWarn>NU1701</NoWarn>
     <RootNamespace>$(MSBuildProjectName.Replace(" ", "_").Replace(".Common", ""))</RootNamespace>

src/Stubs/AssemblyMetadataAttribute.cs

@@ -0,0 +1,20 @@
+#if NET35 || NET40
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
+    public class AssemblyMetadataAttribute : Attribute
+    {
+        public string Key { get; protected set; }
+
+        public string Value { get; protected set; }
+
+        public AssemblyMetadataAttribute(string key, string value)
+        {
+            Key = key;
+            Value = value;
+        }
+    }
+}
+
+#endif