Feature: #28382 - Add async property to JavaScript files

See Issue #28382

Description

Add a property async="async" to JavaScript files via TypoScript

page.includeJSlibs.<array>.async = 1

This patch affects the TypoScript PAGE properties

• includeJSLibs
• includeJSFooterlibs
• includeJS
• includeJSFooter

Usage:

page {
        includeJS {
                jsFile = /Path/To/jsFile.js
                jsFile.async = 1
        }
}