Adds missing Swift fileprivate access modifier

As per https://docs.swift.org/swift-book/LanguageGuide/AccessControl.html#ID5

src/swift/swift.ts

@@ -55,7 +55,7 @@ export const language = <languages.IMonarchLanguage>{
 		'@IBInspectable',
 		'@IBOutlet'
 	],
-	accessmodifiers: ['public', 'private', 'internal'],
+	accessmodifiers: ['public', 'private', 'fileprivate', 'internal'],
 	keywords: [
 		'__COLUMN__',
 		'__FILE__',