Add giveConfig to ContextualBindingBuilder (#39819)

Author: simensen

src/Illuminate/Contracts/Container/ContextualBindingBuilder.php

@@ -27,4 +27,13 @@ public function give($implementation);
      * @return void
      */
     public function giveTagged($tag);
+
+    /**
+     * Specify the configuration item to bind as a primitive.
+     *
+     * @param  string  $key
+     * @param  ?string  $default
+     * @return void
+     */
+    public function giveConfig($key, $default = null);
 }