Vulkan: add docs for the framework generation scripts

Bug: 134185757
Test: ./scripts/code_generator.py && build
Change-Id: I108412fdc672c5513f570ddac9221074a0027cd0
diff --git a/vulkan/scripts/code_generator.py b/vulkan/scripts/code_generator.py
index 378a9c0..2a017d2 100755
--- a/vulkan/scripts/code_generator.py
+++ b/vulkan/scripts/code_generator.py
@@ -13,9 +13,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
-# This script provides the main function for generating
-# vulkan framework directly from the vulkan registry (vk.xml).
+
+"""Generates vulkan framework directly from the vulkan registry (vk.xml).
+"""
 
 import api_generator
 import driver_generator