Document YOURLS_USER and YOURLS_PASS for YOURLS image

Fix YOURLS/docker-yourls#19

yourls/content.md

@@ -11,6 +11,8 @@ YOURLS is a set of PHP scripts that will allow you to run Your Own URL Shortener
 ```console
 $ docker run --name some-%%REPO%% --link some-mysql:mysql \
     -e YOURLS_SITE="https://example.com" \
+    -e YOURLS_USER="example_username" \
+    -e YOURLS_PASS="example_password" \
     -d %%IMAGE%%
 ```
 
@@ -23,6 +25,8 @@ The following environment variables are also honored for configuring your YOURLS
 -	`-e YOURLS_TABLE_PREFIX=...` (defaults to "", only set this when you need to override the default table prefix in wp-config.php)
 -	`-e YOURLS_COOKIEKEY=...` (default to unique random SHA1s)
 -	`-e YOURLS_SITE=...` (yourls instance url)
+-	`-e YOURLS_USER=...` (yourls instance user name)
+-	`-e YOURLS_PASS=...` (yourls instance user password)
 
 If the `YOURLS_DB_NAME` specified does not already exist on the given MySQL server, it will be created automatically upon startup of the `yourls` container, provided that the `YOURLS_DB_USER` specified has the necessary permissions to create it.
 

yourls/stack.yml

@@ -10,6 +10,8 @@ services:
     environment:
       YOURLS_DB_PASS: example
       YOURLS_SITE: https://example.com
+      YOURLS_USER: example_username
+      YOURLS_PASS: example_password
 
   mysql:
     image: mysql:5.7