Update CHANGELOG.md for 2.0.0-dev.63 release

Change-Id: I8ee73624eddf5a5698a6a89db691b530de694102
Reviewed-on: https://dart-review.googlesource.com/60420
Reviewed-by: Nate Bosch <nbosch@google.com>
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f8e4540..beb9682 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,12 +12,18 @@
 
 #### Pub
 
-* Fix an error which prevented `pub publish` due to the package validation.
-
 #### Other Tools
 
 ### Core library changes
 
+## 2.0.0-dev.63.0
+
+### Tool Changes
+
+#### Pub
+
+* Fix an error which prevented `pub publish` due to the package validation.
+
 ## 2.0.0-dev.62.0
 
 ### Language