fix(app-project): publish /robots.txt for the projects app (#6335)

Rewrite `/robots.txt` as `/projects/robots.txt` so that projects staging deploys are hidden behind a `robots.txt` file at https://fe-project.zooniverse.org/robots.txt

Co-authored-by: Delilah C. <[email protected]>

packages/app-project/middleware.js

@@ -35,6 +35,14 @@ export function middleware(req, event) {
     return NextResponse.next()
   }
 
+  /*
+    Serve /projects/robots.txt as /robots.txt.
+  */
+  if (pathname === '/robots.txt') {
+    url.pathname = '/projects/robots.txt'
+    return NextResponse.rewrite(url)
+  }
+
   /*
     Redirect /projects/[owner]/[project]?language=[lang] to /projects/[lang]/[owner]/[project].
   */