[gimp] NEWS: mention enum docs in libgimpbase

[Michael Natterer <mitch src gnome org>]

commit dca90f303b43f520e10627468f1439dc6816bfa0
Author: Michael Natterer <mitch gimp org>
Date:   Sun May 20 16:42:12 2018 +0200

    NEWS: mention enum docs in libgimpbase

 NEWS |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/NEWS b/NEWS
index 627787c..0535f53 100644
--- a/NEWS
+++ b/NEWS
@@ -71,3 +71,5 @@ Documentation:
 
   - Updating the description of the XCF format "devel-docs/xcf.txt", for
     third-party readers wishing to support GIMP 2.10 XCF files.
+  - Add documentation skeletons for all enums in libgimpbase/, there is
+    much room for improvement.