add WorkshopDL support

README.md

@@ -67,7 +67,8 @@ docker run -it \
     -e "AUTHKEY=..." \
     -e "GAMEMODE=terrortown" \
     -e "MAP=ttt_minecraft_b5" \
-    -e "WORKSHOPCOLLECTIONID=843519054" \
+    -e "WORKSHOP=843519054" \
+    -e "WORKSHOPDL=843519054" \
     -v ./server.cfg:/opt/steam/garrysmod/cfg/server.cfg \
     hackebein/garrysmod
 ```
@@ -94,6 +95,12 @@ MAXPLAYERS: Max players
 CUSTOMPARAMETERS: additional parameters
 (`Default: `)
 
+WORKSHOP: downloads workshop collection for server
+(`Default: `)
+
+WORKSHOPDL: downloads workshop collection for client before joining
+(`Default: `)
+
 ## More Options
 
 You can found more configuration options on the parent image page [hackebein/srcds](https://hub.docker.com/r/hackebein/srcds)