docs: update readme (#17)

Signed-off-by: Andrew Brandt <andrew.brandt@hashgraph.com>
Co-authored-by: Roger Barker <roger.barker@swirldslabs.com>

Author: andrewb1269hg

README.md

@@ -1,2 +1,87 @@
-# update-custom-props
-Github Action to Update Custom Properties in a Workflow
+# README for the project Update Custom Properties
+
+**Update custom properties for all repos in an organization from a YAML file.**
+
+This action uses the GitHub CLI to read values from `repo-properties.yaml` and update repos in the organization. This
+can be useful for easily maintaining a single source of truth and a git-based history of updates to the
+custom properties of the organization.
+
+---
+
+## 🚀 Getting Started
+
+1. Add this GitHub Action to your workflow.
+2. Run the workflow. The file `repo-properties.yaml` will automatically be parsed and all appropriate repo values
+will be updated.
+
+---
+
+## Fine Grained Token Requirements
+
+To run the action within your GitHub CI/CD pipeline you will need to create a
+fine-grained token with the following permissions:
+
+### Organization Permissions
+
+- Read and Write access to repository custom properties
+
+### Additional Information
+
+- [GitHub API for custom property for an organization](https://docs.github.com/en/rest/orgs/custom-properties?apiVersion=2022-11-28#create-or-update-a-custom-property-for-an-organization)
+- [Fine-grained personal access tokens](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/managing-your-personal-access-tokens#creating-a-fine-grained-personal-access-token)
+- The owner of the fine-grained token must have full administrative rights to the organization.
+
+---
+
+## 📦 Inputs
+
+| Name                   | Description                                                                                           | Required | Default                |
+|------------------------|-------------------------------------------------------------------------------------------------------|----------|------------------------|
+| `token`                | GitHub Personal Access Token (Fine-Grained with: Repository custom properties `Read and Write` scope) | ✅ Yes    | —                      |
+| `repo-properties.yaml` | File should be located in the root-level directory.                                                   | ✅ Yes    | `repo-properties.yaml` |
+
+---
+
+## 🛠 Usage
+
+```yaml
+jobs:
+  update-schema:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: PandasWhoCode/update-custom-properties@v1
+        with:
+          token: ${{ secrets.GH_CUSTOM_PROPERTIES_TOKEN }}
+```
+
+---
+
+## Example custom_props.json
+
+`custom_props.json`:
+```yaml
+org: PandasWhoCode
+repositories:
+  - name: my-example-repo
+    last-date-modified: ""
+    initial-ci-review-by-team: "pandas"
+    initial-ci-review-date: "2025-04-07"
+    initial-security-review-by-team: "admins"
+    initial-security-review-date: "2025-04-15"
+    last-security-review-by-team: "reviewers"
+    last-security-review-date: "2025-05-01"
+```
+
+---
+
+## 👤 Author
+
+Andrew Brandt
+
+[PandasWhoCode](https://pandaswhocode.com)
+
+[andrew.brandt@pandaswhocode.com](mailto:andrew.brandt@pandaswhocode.com)
+
+---