extensions/markdown-language-features/preview-src/csp.ts/CspAlerter/showCspWarning
class CspAlerter:	private showCspWarning() {
		const strings = getStrings();
		const settings = getSettings();

		if (this.didShow || settings.disableSecurityWarnings || !this.messaging) {
			return;
		}
		this.didShow = true;

		const notification = document.createElement('a');
		notification.innerText = strings.cspAlertMessageText;
		notification.setAttribute('id', 'code-csp-warning');
		notification.setAttribute('title', strings.cspAlertMessageTitle);

		notification.setAttribute('role', 'button');
		notification.setAttribute('aria-label', strings.cspAlertMessageLabel);
		notification.onclick = () => {
			this.messaging!.postMessage('showPreviewSecuritySelector', { source: settings.source });
		};
		document.body.appendChild(notification);
	}