Add README

README.md

@@ -1 +1,25 @@
-# github-app
+# Authenticate as a GitHub App
+
+This library provides functions that help with authenticating as a [GitHub App][ghapp].
+
+
+## Use
+
+1. [Register][reg] your App with GitHub to obtain an App ID and a private key.
+2. Using the data from the step above, create `AppAuth`.
+3. For each installation of your app, get an `InstallationAuth` using `mkInstallationAuth`.
+4. Use the `executeAppRequest` function to execute requests.
+   Behind the scenes, this function exchanges the installation auth token for
+   a regular access token, caches it, and renews as needed.
+
+See [serokell/github-ops-access][ghopsa] for a real-life example use.
+
+[ghapp]: https://developer.github.com/apps/
+[reg]: https://github.com/settings/apps
+[ghopsa]: https://github.com/serokell/github-ops-access/blob/test/webhook/Main.hs
+
+
+## About Serokell
+
+This library is maintained and funded with ❤️ by [Serokell](https://serokell.io/).
+The names and logo for Serokell are trademark of Serokell OÜ.