Function prepare_javascript_frontend 

pub fn prepare_javascript_frontend(
    workspace: &Path,
    project: &CoverageProject,
    collector_id: &str,
    cache_key: &str,
    command: &[String],
) -> Result<PreparedJavascriptFrontend, JavascriptFrontendError>

Prepare the complete JavaScript frontend inside an isolated workspace. The source project is read only through the copied workspace inventory.