Add marketplace badge

.github/badges/trustabl-action.json

@@ -0,0 +1,6 @@
+{
+  "schemaVersion": 1,
+  "label": "used by",
+  "message": "0",
+  "color": "blue"
+}

.github/workflows/count-action-users.yml

@@ -0,0 +1,28 @@
+name: Count action users
+
+# Counts public repos whose workflow files reference this action (GitHub
+# code search) and writes a shields.io endpoint JSON that the README
+# "used by" badge renders. Public workflow files only; a proxy for adoption.
+
+on:
+  schedule:
+    - cron: '0 4 * * 1'   # weekly, Mondays 04:00 UTC
+  workflow_dispatch:        # run on demand to populate the badge immediately
+
+permissions:
+  contents: write           # the action commits the generated badge JSON
+
+jobs:
+  count:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Generate "used by" badge endpoint
+        uses: cicirello/count-action-users@v1
+        with:
+          action-list: trustabl/trustabl-action
+          target-directory: .github/badges
+          commit-and-push: true
+          color: blue
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

README.md

@@ -2,6 +2,12 @@
   <img src="assets/github_banner.jpg" alt="Trustabl — open-source tooling for production-ready agentic tools" width="100%">
 </p>
 
+<p align="center">
+  <a href="https://github.com/marketplace/actions/trustabl"><img src="https://img.shields.io/badge/GitHub%20Marketplace-Trustabl-2088FF?logo=githubactions&logoColor=white" alt="Trustabl on GitHub Marketplace"></a>
+  <a href="https://github.com/trustabl/trustabl/releases"><img src="https://img.shields.io/github/downloads/trustabl/trustabl/total?logo=github&label=downloads&color=2088FF" alt="trustabl binary downloads"></a>
+  <a href="https://github.com/search?q=uses%3A+trustabl%2Ftrustabl-action+path%3A.github%2Fworkflows&type=code"><img src="https://img.shields.io/endpoint?url=https%3A%2F%2Fraw.githubusercontent.com%2Ftrustabl%2Ftrustabl-action%2Fmain%2F.github%2Fbadges%2Ftrustabl-action.json" alt="Used by (repos)"></a>
+</p>
+
 # Trustabl Action
 
 A GitHub Action that runs [trustabl](https://github.com/trustabl/trustabl) — the