add BatchSize property to serverless MSKEvent

[royffeng]

fixes #2324

[markpeek]

Thank you for the PR. I noticed some other missing properties in there as well. Would you like to add these as well to your PR?

diff --git a/troposphere/serverless.py b/troposphere/serverless.py
index 3082f504..27a510c1 100644
--- a/troposphere/serverless.py
+++ b/troposphere/serverless.py
@@ -21,6 +21,7 @@ from .awslambda import (
     ProvisionedConcurrencyConfiguration,
     ProvisionedPollerConfig,
     RuntimeManagementConfig,
+    SchemaRegistryConfig,
     SnapStart,
     SourceAccessConfiguration,
     VPCConfig,
@@ -731,8 +732,10 @@ class MSKEvent(AWSObject):
         "ConsumerGroupId": (str, False),
         "DestinationConfig": (DestinationConfig, False),
         "FilterCriteria": (FilterCriteria, False),
+        "KmsKeyArn": (str, False),
         "MaximumBatchingWindowInSeconds": (integer, False),
         "ProvisionedPollerConfig": (ProvisionedPollerConfig, False),
+        "SchemaRegistryConfig": (SchemaRegistryConfig, False),
         "SourceAccessConfigurations": ([SourceAccessConfiguration], False),
         "StartingPosition": (str, True),
         "StartingPositionTimestamp": (double, False),

[royffeng]

added SchemaRegistryConfig and KmsKeyArn!

[markpeek]

Thank you for the PR and adding the other missing properties.