Add default value to SECRET_KEY

Dockerfile

@@ -1,7 +1,7 @@
 FROM richarvey/nginx-php-fpm
 
 ENV WEBROOT="/webroot"
-ENV SECRET_KEY
+ENV SECRET_KEY="a1b2c3d4e5f6g7h8i9j0k"
 
 RUN mkdir ${WEBROOT} && mkdir /storage
 

README.md

@@ -9,7 +9,7 @@ It just serves a simple file named share_v2.php taken from [Prosody's source](ht
 This server is ment to be used in conjuntion with Prosody XMPP server and *mod\_http\_upload\_external* ([docs](https://modules.prosody.im/mod_http_upload_external.html))
 
 ## Variables
-* SECRET\_KEY: Stores the secret key shared with the prosody server (http\_upload\_external\_secret option)
+* SECRET\_KEY: Stores the secret key shared with the prosody server (http\_upload\_external\_secret option). Defaults to "a1b2c3d4e5f6g7h8i9j0k"
 
 ## Volumes
 * /storage: Used to store and serve the uploaded files