Fix missing doxygen on enum warning

Change-Id: I4e3b22e64554427f341a1bb260d72aa202c6b53c
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/42027
Auto-Submit: Ben Clayton <bclayton@google.com>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>

src/inspector/inspector.h

diff --git a/src/inspector/inspector.h b/src/inspector/inspector.h
index eeab561..db9c3c0 100644
--- a/src/inspector/inspector.h
+++ b/src/inspector/inspector.h
@@ -55,6 +55,7 @@
   /// in SPIR-V OpTypeImage.
   enum class SampledKind { kUnknown = -1, kFloat, kUInt, kSInt };
 
+  /// Enumerator of texture image formats
   enum class ImageFormat {
     kNone = -1,
     kR8Unorm,