chore: exclude .NET metadata from UPM packages

.npmignore

@@ -10,3 +10,5 @@ DotNet~/
 Godot~/
 NuGet.Config
 Directory.Build.props
+NuGet.Config.meta
+Directory.Build.props.meta

Directory.Build.props.meta

@@ -0,0 +1,7 @@
+fileFormatVersion: 2
+guid: aaa406cc3ac2e884da352357feb34b9b
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

NuGet.Config.meta

@@ -0,0 +1,32 @@
+fileFormatVersion: 2
+guid: 3fbea28f1ed845645957b24bbd951127
+PluginImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  iconMap: {}
+  executionOrder: {}
+  defineConstraints: []
+  isPreloaded: 0
+  isOverridable: 0
+  isExplicitlyReferenced: 0
+  validateReferences: 1
+  platformData:
+  - first:
+      Any: 
+    second:
+      enabled: 0
+      settings: {}
+  - first:
+      Editor: Editor
+    second:
+      enabled: 0
+      settings:
+        DefaultValueInitialized: true
+  - first:
+      Windows Store Apps: WindowsStoreApps
+    second:
+      enabled: 1
+      settings: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: