Revert "Delete global.json"

This reverts commit 261215b.

Author: nohwnd

global.json

@@ -0,0 +1,15 @@
+{
+  "sdk": {
+    "version": "3.1.101",
+    "rollForward": "minor",
+    "allowPrerelease": false,
+    "architecture": "x64"
+  },
+  "tools": {
+    "dotnet": "3.1.101"
+  },
+  "msbuild-sdks": {
+    "Microsoft.DotNet.Arcade.Sdk": "5.0.0-beta.20052.1",
+    "Microsoft.DotNet.Helix.Sdk": "5.0.0-beta.20052.1"
+  }
+}