Support configuration without config file

README.md

@@ -8,3 +8,17 @@
  * Lightweight and fast: __over 9000 requests per second__ on a standard laptop
 
 https://od-db.the-eye.eu/
+
+#### Usage
+
+ 1. With Config File (if `config.yml` found in working dir)
+    - Download [default config](https://github.com/terorie/od-database-crawler/blob/master/config.yml)
+    - Set `server.url` and `server.token`
+    - Start with `./od-database-crawler server --config <file>`
+ 
+ 2. With Flags or env
+    - Override config file if it exists
+    - `--help` for list of flags
+    - Every flag is available as an environment variable:
+      `--server.crawl_stats` ➡️ `OD_SERVER_CRAWL_STATS`
+    - Start with `./od-database-crawler server <flags>`