Add nuspec for the IL2CPP version

Author: ManlyMarco

ConfigurationManager.IL2CPP/ConfigurationManager.IL2CPP.nuspec

@@ -0,0 +1,14 @@
+<?xml version="1.0"?>
+<package >
+  <metadata>
+    <id>BepInEx.ConfigurationManager.IL2CPP</id>
+    <version>$version$</version>
+    <authors>ManlyMarco</authors>
+    <projectUrl>https://github.com/BepInEx/BepInEx.ConfigurationManager</projectUrl>
+    <requireLicenseAcceptance>false</requireLicenseAcceptance>
+    <description>Plugin configuration manager for BepInEx 6 (IL2CPP, bleeding edge)</description>
+    <dependencies>
+      <group targetFramework="net6.0" />
+    </dependencies>
+  </metadata>
+</package>

ConfigurationManager/ConfigurationManager.nuspec

@@ -6,7 +6,7 @@
     <authors>ManlyMarco</authors>
     <projectUrl>https://github.com/BepInEx/BepInEx.ConfigurationManager</projectUrl>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
-    <description>Plugin configuration manager for BepInEx</description>
+    <description>Plugin configuration manager for BepInEx 5</description>
     <developmentDependency>true</developmentDependency>
   </metadata>
   <files>