[x/go.dev] all: render nested index.html pages on appengine

This change allows requests like /post or /learn to render the
appropriate index.html file, while still being able to return files from
the css and images directory.
X-GoDev-Commit: e5eab4362ab3c9d3399db32d64a7a90a8eb6a8ea
diff --git a/go.dev/app.yaml b/go.dev/app.yaml
index e61c436..9227cf2 100644
--- a/go.dev/app.yaml
+++ b/go.dev/app.yaml
@@ -8,6 +8,13 @@
   static_files: public/index.html
   upload: public/index.html
 
-- url: /(.*)
-  static_files: public/\1
+# Special for static content so we do not try to append index.html to their paths.
+- url: /(css|images)/(.*)
+  static_files: public/\1/\2
   upload: public/(.*)
+
+# Handle arbitrary paths with an index.html
+- url: /(.*)
+  static_files: public/\1/index.html
+  upload: public/(.*)/index.html
+