add function description

src/SPC/builder/Extension.php

@@ -203,6 +203,15 @@ class Extension
         return false;
     }
 
+    /**
+     * @return string
+     *  returns a command line string with all required shared extensions to load
+     *  i.e.; pdo_pgsql would return:
+     *
+     * `-d "extension=pgsql" -d "extension=pdo_pgsql"`
+     * @throws FileSystemException
+     * @throws WrongUsageException
+     */
     public function getRequiredSharedExtensions(): string
     {
         $loaded = [];