Improve docs für aggregator

docs/csaf_aggregator.md

@@ -15,6 +15,35 @@ Help Options:
   -h, --help               Show this help message
 ```
 
-
 Usage example:
 ``` ./csaf_aggregator -c docs/examples/aggregator.toml ```
+
+### config options
+
+*todo*
+
+```
+workers
+folder
+web
+domain
+rate
+insecure
+aggregator
+providers
+key
+openpgp_url
+passphrase
+allow_single_provider
+lock_file
+interim_years
+```
+
+`providers` is a list of tables, each allowing
+```
+name
+domain
+rate
+insecure
+```
+