[CustomConfiguration] Add "Authentication"

Custom-Configuration.md

@@ -14,15 +14,18 @@ __Notice__: If a parameter is not specified in your `config.ini.php` RSS-Bridge
 
 # Available parameters
 
-The configuration file is split into two sections:
+The configuration file is split into three sections:
 
 * [cache](#cache)
 * [proxy](#proxy)
+* [authentication](#authentication)
 
 _Cache_: This section is all about the caching behaviour of RSS-Bridge
 
 _Proxy_: This section can be used to specify a proxy server for RSS-Bridge to utilize for fetching contents
 
+_Authentication_: This section defines parameters to require authentication to use RSS-Bridge
+
 ## Cache
 
 This section provides following parameters:
@@ -64,3 +67,29 @@ Allow users to disable proxy usage for specific requests.
 `true`  = enabled
 
 `false` = disabled (default)
+
+## Authentication
+
+This section provides following parameters:
+
+- [enable](#enable)
+- [username](#username)
+- [password](#password)
+
+### enable
+
+Enables authentication for RSS-Bridge.
+
+_Notice_: Login is required for all requests when enabled! Make sure to update feed subscriptions accordingly.
+
+`true`  = enabled
+
+`false` = disabled (default)
+
+### username
+
+Defines the user name used for login.
+
+### password
+
+Defines the password used for login. Use a strong password to prevent others from guessing your login!