docs: Fix typos in mapping document

Author: jskeet

docs/mapping.md

@@ -141,8 +141,8 @@ This will lead to CloudEvent attributes of:
 
 ### Cloud PubSub events
 
-The GCF HTTP representation of Cloud Storage events (events with a
-*gcf_service* of `storage.googleapis.com`) contain a `data` property
+The GCF HTTP representation of Cloud PubSub events (events with a
+*gcf_service* of `pubsub.googleapis.com`) contain a `data` property
 which needs to be wrapped in an extra JSON object in the CloudEvent
 `data` attribute, to conform with the [expected CloudEvent
 representation](https://github.com/googleapis/google-cloudevents/blob/master/proto/google/events/cloud/pubsub/v1/data.proto).
@@ -160,7 +160,7 @@ Additionally, two properties should be populated in the message,
 based on the context:
 
 - The `messageId` property in the `message` object should be set to *gcf_event_id*
-- The `publishTime` proeprty in the `message` object should be set to *gcf_timestamp*
+- The `publishTime` property in the `message` object should be set to *gcf_timestamp*
 
 The conversion should **not** parse *gcf_data* to ensure that only
 expected properties are present. (For example, the GCF HTTP