Update readme

README.md

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 # decap-cms-github-oauth-api-cloudflare-worker
 
-A github oauth authentication gateway for Decap CMS login, runnable as a cloudflare worker
+A github oauth authentication gateway for [Decap CMS](https://github.com/decaporg/decap-cms) login, runnable as a cloudflare worker
+
+Use case - you want to use your Github repo as a CMS with Decap CMS, but don't want to rely on Netlify authentication backend. You can host this service on a cloudflare worker to authenticate with Github without a 3rd party.
+
+## Setup
+
+1. [Create a github app](https://docs.github.com/en/apps/creating-github-apps/registering-a-github-app/registering-a-github-app)
+2. Fork this repository
+3. [Create a cloudflare account](https://dash.cloudflare.com/) if you don't have one
+
+4. Install the (Cloudflare) `wrangler` CLI and login with your account
+
+```
+npm install --global wrangler
+wrangler login
+```
+
+5. Edit the `wrangler.toml` file, change the value for account_id to your own (`wrangler whoami` shows account ID)
+
+6. Add the following secrets to your Cloudflare worker:
+
+   `CLIENT_ID`, `CLIENT_SECRET`: In your GitHub App's settings page, find the Client ID and generate a Client Secret
+
+```
+   wrangler secret put CLIENT_ID
+   wrangler secret put CLIENT_SECRET
+```
+
+7. Configure Github action for deploying the worker – create a new [Cloudflare API token](https://dash.cloudflare.com/profile/api-tokens)(Use "Edit Cloudflare Workers" template) and add it as a secret in your fork's repository settings->secrets->actions.
+
+## Credits
+
+Inspiration from:
+
+- https://github.com/gr2m/cloudflare-worker-github-oauth-login
+- https://github.com/vencax/netlify-cms-github-oauth-provider