fix: move VS Marketplace badge to Visual Studio Extension section (#585)

* fix: move VS Marketplace badge to Visual Studio Extension section

The RobBos.AIEngineeringFluency badge was mistakenly placed at the top
of the README alongside the Build badge. It now lives under the
Visual Studio Extension section where it belongs.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: replace deprecated shields.io VS Marketplace badges with vsmarketplacebadges.dev

shields.io dropped VS Marketplace support (badges/shields#11792) because
Microsoft does not publicly document the API and it cannot be used by
third-party services.

Switch both extension badges to vsmarketplacebadges.dev which is the
dedicated community replacement. Tested: both SVGs resolve with live
install counts before committing.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Update README to remove token count estimation note

Removed note about estimated token counts from README.

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: rajbos

README.md

@@ -5,7 +5,6 @@
 Track your GitHub Copilot token usage and AI Fluency across VS Code, Visual Studio, and the command line. All data is read from local session logs — nothing leaves your machine unless you opt in to cloud sync.
 
 [![Build](https://github.com/rajbos/github-copilot-token-usage/actions/workflows/build.yml/badge.svg)](https://github.com/rajbos/github-copilot-token-usage/actions/workflows/build.yml)
-[![Visual Studio Marketplace Downloads](https://img.shields.io/visual-studio-marketplace/d/RobBos.AIEngineeringFluency)](https://marketplace.visualstudio.com/items?itemName=RobBos.AIEngineeringFluency)
 
 ## Supported AI engineering tools
 
@@ -26,7 +25,7 @@ Track your GitHub Copilot token usage and AI Fluency across VS Code, Visual Stud
 
 Real-time token usage in the status bar, fluency score dashboard, usage analysis, cloud sync, and more.
 
-[![Visual Studio Marketplace Downloads](https://img.shields.io/visual-studio-marketplace/d/RobBos.copilot-token-tracker)](https://marketplace.visualstudio.com/items?itemName=RobBos.copilot-token-tracker)
+[![Visual Studio Marketplace Installs](https://vsmarketplacebadges.dev/installs-short/RobBos.copilot-token-tracker.svg)](https://marketplace.visualstudio.com/items?itemName=RobBos.copilot-token-tracker)
 
 ```bash
 # Install from the VS Code Marketplace
@@ -41,7 +40,7 @@ ext install RobBos.copilot-token-tracker
 
 Token usage tracking inside Visual Studio 2022+, reading Copilot Chat session files directly.
 
-> Counts are **estimated** — VS session files do not store raw LLM token counts.
+[![Visual Studio Marketplace Installs](https://vsmarketplacebadges.dev/installs-short/RobBos.AIEngineeringFluency.svg)](https://marketplace.visualstudio.com/items?itemName=RobBos.AIEngineeringFluency)
 
 📖 [Full Visual Studio extension documentation](docs/visual-studio/README.md)