docs: add FOSSA badge to README

Use shields.io static badge to link to the FOSSA project page.
The native FOSSA SVG badge URL is blocked by vsce packaging.

Signed-off-by: Sebastien Tardif <sebtardif@ncf.ca>

Author: SebTardif

README.md

@@ -7,6 +7,7 @@
 [![CI](https://github.com/patchloom/patchloom-vscode/actions/workflows/ci.yml/badge.svg)](https://github.com/patchloom/patchloom-vscode/actions/workflows/ci.yml)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://github.com/patchloom/patchloom-vscode/blob/main/LICENSE)
 [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/patchloom/patchloom-vscode/badge)](https://securityscorecards.dev/viewer/?uri=github.com/patchloom/patchloom-vscode)
+[![FOSSA Status](https://img.shields.io/badge/license%20scan-FOSSA-blue)](https://app.fossa.com/projects/git%2Bgithub.com%2Fpatchloom%2Fpatchloom-vscode)
 
 The official VS Code extension for [Patchloom](https://github.com/patchloom/patchloom). Set up your workspace for AI agent workflows in seconds: detect the CLI, generate agent rules, configure MCP servers, and run structured file operations from the command palette.