fix: Use .NET 9 SDK (#323)

Author: skarllot

.github/workflows/package.yml

@@ -42,6 +42,10 @@ jobs:
       - name: 🧰 Setup .NET
         uses: actions/setup-dotnet@67a3573c9a986a3f9c594539f4ab511d57bb3ce9 # v4.3.1
         with:
+          dotnet-version: |
+            6.x
+            8.x
+            9.x
           global-json-file: global.json
 
       - name: 🗃️ Setup NuGet cache

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "8.0.410",
+    "version": "9.0.300",
     "rollForward": "latestMajor",
     "allowPrerelease": false
   }