add initial docs

README.md

@@ -1,4 +1,21 @@
 # rss2twitter - [![Build Status](https://travis-ci.org/umputun/rss2twitter.svg?branch=master)](https://travis-ci.org/umputun/rss2twitter) [![Docker Automated build](https://img.shields.io/docker/automated/jrottenberg/ffmpeg.svg)](https://hub.docker.com/r/umputun/rss2twitter/)
 
-Publishes RSS updates to twitter
+The service publishes RSS updates to twitter. 
 
+## install
+
+Use provided `docker-compose.yml` and change `FEED` value. All twiter-api credentials can be retrieved from https://developer.twitter.com/en/apps and should be set in environment or directly in the compose file.
+
+## parameters
+
+```
+Application Options:
+  -r, --refresh=         refresh interval (default: 30s) [$REFRESH]
+  -t, --timeout=         twitter timeout (default: 5s) [$TIMEOUT]
+  -f, --feed=            rss feed url [$FEED]
+      --consumer-key=    twitter consumer key [$CONSUMER_KEY]
+      --consumer-secret= twitter consumer secret [$CONSUMER_SECRET]
+      --access-token=    twitter access token [$ACCESS_TOKEN]
+      --access-secret=   twitter access secret [$ACCESS_SECRET]
+      --dbg              debug mode [$DEBUG]
+```