docs: backfill change notes

0.37.4 was only intended to fix the github.com/golang/lint problem, but
we inadvertently created a release that exposed a fair amount of work
since 0.37.2 (0.37.3 is a throw-away, since the go.sum is broken in it).

This CL backfills the changes in CHANGES.md.

Seeing how many changes there are, we probably should have done a minor
release instead of a patch. But, that's ok - it doesn't necessarily harm
anyone.

This commit will _not_ be tagged, since it is only a backfill and not
a new release.

Change-Id: I9ea5d174dcf25f4058f230e63e89dbdf5f8abc79
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/39770
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
diff --git a/CHANGES.md b/CHANGES.md
index a3feea3..2970b5c 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -5,6 +5,29 @@
 This patch releases re-builds the go.sum. This was not possible in the
 previous release.
 
+- firestore:
+  - Add sentinel value DetectProjectID for auto-detecting project ID.
+  - Add OpenCensus tracing for public methods.
+  - Marked stable. All future changes come with a backwards compatibility
+  guarantee.
+  - Removed firestore/apiv1beta1. All users relying on this low-level library
+  should migrate to firestore/apiv1. Note that most users should use the
+  high-level firestore package instead.
+- pubsub:
+  - Allow large messages in synchronous pull case.
+  - Cap bundler byte limit. This should prevent OOM conditions when there are
+  a very large number of message publishes occurring.
+- storage:
+  - Add ETag to BucketAttrs and ObjectAttrs.
+- datastore:
+  - Removed some non-sensical OpenCensus traces.
+- webrisk:
+  - Add v1 client.
+- asset:
+  - Add v1 client.
+- cloudtasks:
+  - Add v2 client.
+
 ## 0.37.3
 
 This patch release removes github.com/golang/lint from the transitive