update readme

readme.md

@@ -1,2 +1,17 @@
 # Prayercal
 
+Generates prayer times daily using [London Prayer Times](https://www.londonprayertimes.com/) API and exposes them as an ical feed daily.
+
+## Install/Build
+
+```bash
+docker run -d -p 5543:5543 uthmn/prayercal:latest
+```
+
+or you can git clone and build it yourself via `go build .`
+
+make sure in the same directory as the executable or the env variables contain `LPT_API_KEY` with your API key.
+
+## Usage
+
+On port 5543 you can access the ical feed at `/prayercal.ics` to import into your calendar.