Adding robots.txt override via admin control panel

This is a requested low priority feature in #418 - I created the changes
to follow similarly to how the Instance Description is handled.

packages/backend/src/core/entities/MetaEntityService.ts

@@ -95,6 +95,7 @@ export class MetaEntityService {
 			mcaptchaInstanceUrl: instance.mcaptchaInstanceUrl,
 			enableRecaptcha: instance.enableRecaptcha,
 			enableAchievements: instance.enableAchievements,
+			robotsTxt: instance.robotsTxt,
 			recaptchaSiteKey: instance.recaptchaSiteKey,
 			enableTurnstile: instance.enableTurnstile,
 			turnstileSiteKey: instance.turnstileSiteKey,