feat: Add mcp.json to Visual Studio gitignore exceptions

As mcp's are becoming more common, sharing a workspace configuration of mcp servers is becoming more and more common with the mcp.json file. (https://code.visualstudio.com/docs/copilot/customization/mcp-servers#_add-an-mcp-server)

Adding this file as an exclusion to the default template so that it can be utilized by the editors and shared via source control.

This file can also be picked up by Visual Studio as seen [here](https://learn.microsoft.com/visualstudio/ide/mcp-servers?view=vs-2022&WT.mc_id=8B97120A00B57354#file-locations-for-automatic-discovery-of-mcp-configuration)

VisualStudio.gitignore

@@ -412,6 +412,7 @@ FodyWeavers.xsd
 !.vscode/tasks.json
 !.vscode/launch.json
 !.vscode/extensions.json
+!.vscode/mcp.json
 !.vscode/*.code-snippets
 
 # Local History for Visual Studio Code