feat(config): add missing methods in contract

Author: Alexandre Gérault

src/Illuminate/Contracts/Config/Repository.php

@@ -54,4 +54,34 @@ public function prepend($key, $value);
      * @return void
      */
     public function push($key, $value);
+
+    /**
+     * Get the specified configuration value typed as a string.
+     * If the value isn't a string it should throw an exception.
+     */
+    public function string(string $key): string;
+
+    /**
+     * Get the specified configuration value typed as an array.
+     * If the value isn't an array it should throw an exception.
+     */
+    public function array(string $key): array;
+
+    /**
+     * Get the specified configuration value typed as an integer.
+     * If the value isn't an integer it should throw an exception.
+     */
+    public function integer(string $key): int;
+
+    /**
+     * Get the specified configuration value typed as a boolean.
+     * If the value isn't a boolean it should throw an exception.
+     */
+    public function boolean(string $key): bool;
+
+    /**
+     * Get the specified configuration value typed as a float.
+     * If the value isn't a float it should throw an exception.
+     */
+    public function float(string $key): float;
 }