Update title of CONTRIBUTING.md

Author: shauryemahajanSF

CONTRIBUTING.md

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+# Contributing to Commerce App Registry
+
+Please follow the guidelines below when submitting new or updated commerce app versions to ensure consistency and smooth reviews.
+
+---
+
+## Pull Request Requirements
+
+Each PR **must** include the following items:
+
+### 1. Commerce App ZIP File
+
+Include the packaged app as a ZIP file with the following naming convention:
+
+```
+[appName]-v[appVersion].zip
+```
+
+**Example:**
+```
+avalara-tax-v1.0.0.zip
+```
+
+---
+
+### 2. `manifest.json`
+
+Each PR must include a `manifest.json` file containing the metadata for the app version.
+
+#### Required Fields
+
+The manifest **must** include the following fields:
+
+- `name`
+- `displayName`
+- `domain`
+- `description`
+- `version`
+- `zip`
+- `sha256`
+
+> **Note:** For new versions of an existing app, you must at minimum update the `version`, `zip`, and `sha256` fields.
+
+#### Example `manifest.json`
+
+```json
+{
+  "name": "avalara-tax",
+  "displayName": "Avalara Tax",
+  "domain": "tax",
+  "description": "Sample Avalara tax app",
+  "version": "1.0.0",
+  "zip": "avalara-tax-v1.0.0.zip",
+  "sha256": "492fb0bc3aa5c762c0209bd22375e14ed2af8f672b679d6105232a37fe726a4f"
+}
+```
+
+---
+
+## Brand New Apps
+
+If you are contributing a **brand new app**, you must also create a `catalog.json` file with **exactly** the following content so CI can update it:
+
+```json
+{
+  "latest": {
+    "version": "INIT",
+    "tag": "INIT"
+  },
+  "versions": []
+}
+```
+
+---
+
+## Final Checklist
+
+Before submitting your PR, please verify:
+
+- [ ] ZIP file name follows the required format
+- [ ] `manifest.json` includes all required fields
+- [ ] `version`, `zip`, and `sha256` are updated correctly
+- [ ] `catalog.json` is included for new apps only
+
+