bigtable: release v1.2.0

Change-Id: I332651a85265e8cef0cfa7124f6744b82e5122a4
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/50351
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Chris Cotter <cjcotter@google.com>
diff --git a/bigtable/CHANGES.md b/bigtable/CHANGES.md
index d264e8d..0e98b76 100644
--- a/bigtable/CHANGES.md
+++ b/bigtable/CHANGES.md
@@ -1,16 +1,26 @@
 # Changes
 
+## v1.2.0
+
+- Update cbt usage string.
+
+- Fix typo in cbt tool.
+
+- Ignore empty lines in cbtrc.
+
+- Emulator now rejects microseconds precision.
+
 ## v1.1.0
 
-* Add support to cbt tool to drop all rows from a table.
+- Add support to cbt tool to drop all rows from a table.
 
-* Adds a method to update an instance with clusters.
+- Adds a method to update an instance with clusters.
 
-* Adds StorageType to ClusterInfo.
+- Adds StorageType to ClusterInfo.
 
-* Add support for the `-auth-token` flag to cbt tool.
+- Add support for the `-auth-token` flag to cbt tool.
 
-* Adds support for Table-level IAM, including some bug fixes.
+- Adds support for Table-level IAM, including some bug fixes.
 
 ## v1.0.0