fix(schema): added description on esModule

src/options.json

@@ -58,6 +58,7 @@
       ]
     },
     "esModule": {
+      "description": "By default, file-loader generates JS modules that use the ES modules syntax.",
       "type": "boolean"
     }
   },

test/__snapshots__/validate-options.test.js.snap

@@ -14,7 +14,8 @@ exports[`validate options should throw an error on the "emitFile" option with "t
 
 exports[`validate options should throw an error on the "esModule" option with "true" value 1`] = `
 "Invalid options object. File Loader has been initialised using an options object that does not match the API schema.
- - options.esModule should be a boolean."
+ - options.esModule should be a boolean.
+   -> By default, file-loader generates JS modules that use the ES modules syntax."
 `;
 
 exports[`validate options should throw an error on the "name" option with "true" value 1`] = `