Add Readme

Author: WojciechRydel

README.md

@@ -1,2 +1,62 @@
 # gcp-sql-proxy
-Google Cloud Platform SQL Proxy extension
+[Google Cloud Platform SQL Proxy extension](https://github.com/GoogleCloudPlatform/cloud-sql-proxy)
+
+## Why
+
+When working with GCP SQL Proxy, it is a burden to keep configuration for
+different connections easily. This extension allows to define multiple
+connections available to easy pick up. e.g.
+
+having:
+```ini
+# $HOME/.config/gcp-sql-proxy/conf.ini
+[development]
+instances=xxx:xxx:xxx=tcp:15432
+```
+
+we can run
+```bash
+gcp-sql-proxy development
+```
+
+Above command will match the ini section by name and apply all arguments
+defined. It translates to
+```bash
+cloud_sql_proxy -instance=xxx:xxx:xxx=tcp:15432
+```
+
+Since all args of `cloud_sql_proxy` are prefixed with a single dash, the
+extension appends the slash to all parameters defined in the `conf.ini` section.
+
+## Systemd unit support
+
+The extension provides systemd unit template called `gcp-sql-proxy`.
+
+Having a `conf.ini` defined, we can run a proxy as a systemd unit. And launch
+several units as well. For example:
+```ini
+# $HOME/.config/gcp-sql-proxy/conf.ini
+[development]
+instances=xxx:xxx:xxx=tcp:15432
+
+[production]
+instances=yyy:yyy:yyy=tcp:25432
+```
+we can enable and start systemd units
+```bash
+> systemctl --user enable --now gcp-sql-proxy@production
+> systemctl --user enable --now gcp-sql-proxy@development
+```
+Now, we have two units up and running in the background. Each attach GCP SQL
+Proxy to a defined port:
+
+- `production` on port `2543`
+- `development` on port `1543`
+
+
+## Install
+The instalation is for now managed by GNU Stow, so **GNU Stow is required**.
+
+```bash
+> make all
+```