Refactor AttributeInfo into a proto

This is a no-op in functionality, but begins to pave the way for a proto output format for Stardoc.

RELNOTES: None.
PiperOrigin-RevId: 244020123
diff --git a/src/main/java/com/google/devtools/build/skydoc/BUILD b/src/main/java/com/google/devtools/build/skydoc/BUILD
index 8f4b587..f34fda2 100644
--- a/src/main/java/com/google/devtools/build/skydoc/BUILD
+++ b/src/main/java/com/google/devtools/build/skydoc/BUILD
@@ -27,6 +27,7 @@
         "//src/main/java/com/google/devtools/build/skydoc/fakebuildapi/repository:srcs",
         "//src/main/java/com/google/devtools/build/skydoc/fakebuildapi/test:srcs",
         "//src/main/java/com/google/devtools/build/skydoc/rendering:srcs",
+        "//src/main/java/com/google/devtools/build/skydoc/rendering/proto:srcs",
     ],
 )