Update autocompletion for widget configuration access

Follow-up for PR openhab#1698 where I forgot this.

Signed-off-by: Florian Hotze <florianh_dev@icloud.com>

bundles/org.openhab.ui/web/src/components/config/editor/hint-components.js

@@ -105,6 +105,7 @@ function hintExpression (cm, line) {
       list: [
         { text: 'items.', displayText: 'items', description: 'Access to item states' },
         { text: 'props.', displayText: 'props', description: 'Access to the props of the parent root component' },
+        { text: 'config.', displayText: 'config', description: 'Access to the configuration of the current component'},
         { text: 'vars.', displayText: 'vars', description: 'Access to context vars' },
         { text: 'loop.', displayText: 'loop', description: 'Access to oh-repeater loop variables' },
         { text: 'JSON.', displayText: 'JSON', description: 'Access to the JSON object functions' },