Add Vulkan to in-progress section of the landing page.

Change-Id: Ib1f911d1a30921e4d74d405b77f930754a647d17
Reviewed-on: https://chromium-review.googlesource.com/374048
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/README.md b/README.md
index 294f70a..91a4744 100644
--- a/README.md
+++ b/README.md
@@ -8,11 +8,11 @@
 
 ### Level of OpenGL ES support via backing renderers
 
-|                |  Direct3D 9   |  Direct3D 11     |   Desktop GL   |    GL ES      |
-|----------------|:-------------:|:----------------:|:--------------:|:-------------:|
-| OpenGL ES 2.0  |    complete   |    complete      |    complete    |   complete    |
-| OpenGL ES 3.0  |               |    complete      |    complete    |  in progress  |
-| OpenGL ES 3.1  |               |   not started    |   in progress  |  in progress  |
+|                |  Direct3D 9   |  Direct3D 11     |   Desktop GL   |    GL ES      |    Vulkan     |
+|----------------|:-------------:|:----------------:|:--------------:|:-------------:|:-------------:|
+| OpenGL ES 2.0  |    complete   |    complete      |    complete    |   complete    |  in progress  |
+| OpenGL ES 3.0  |               |    complete      |    complete    |  in progress  |  not started  |
+| OpenGL ES 3.1  |               |   not started    |   in progress  |  in progress  |  not started  |
 
 ### Platform support via backing renderers