Rename renovate config back to .json

.json5 was fine, but VS Code doesn't have native support for it, and the popular JSON5 extension doesn't support JSON schema.

.devcontainer/devcontainer.json

@@ -17,8 +17,7 @@
         "dotjoshjohnson.xml",
         "ms-vscode-remote.remote-containers",
         "ms-azuretools.vscode-docker",
-        "tintoy.msbuild-project-tools",
-        "mrmlnc.vscode-json5"
+        "tintoy.msbuild-project-tools"
       ]
     }
   },

.github/renovate.json

@@ -0,0 +1,21 @@
+{
+	"$schema": "https://docs.renovatebot.com/renovate-schema.json",
+	"extends": ["config:recommended"],
+	"semanticCommits": "disabled",
+	"labels": ["dependencies"],
+	"packageRules": [
+		{
+			"matchPackageNames": ["nbgv", "nerdbank.gitversioning"],
+			"groupName": "nbgv and nerdbank.gitversioning updates"
+		},
+		{
+			"matchPackageNames": ["xunit*"],
+			"groupName": "xunit"
+		},
+		{
+			"matchDatasources": ["dotnet-version", "docker"],
+			"matchDepNames": ["dotnet-sdk", "mcr.microsoft.com/dotnet/sdk"],
+			"groupName": "Dockerfile and global.json updates"
+		}
+	]
+}

.vscode/extensions.json

@@ -13,8 +13,7 @@
     "dotjoshjohnson.xml",
     "ms-vscode-remote.remote-containers",
     "ms-azuretools.vscode-docker",
-    "tintoy.msbuild-project-tools",
-    "mrmlnc.vscode-json5"
+    "tintoy.msbuild-project-tools"
   ],
   // List of extensions recommended by VS Code that should not be recommended for users of this workspace.
   "unwantedRecommendations": []