Add Changelog entries to release announcement

docs/announce/2015.12.md

@@ -71,12 +71,36 @@ and the specification. For the latest Rakudo Star release, see
 <http://rakudo.org/downloads/star/>. A Christmas-based version will
 be available soon.
 
-Some of the changes in this release are outlined below:
+In addition to being our Christmas release, this is yet another
+monthly compiler release; Some of the changes that are new in
+release are outlined below:
 
 New in 2015.12:
-   + Christmas!
+ + Fixed size and multi-dimensional typed and native arrays
+ + Greatly overhauled module loading and installation, including handling
+   precompilation at module installation time in Rakudo
+ + while/until loops can now return lists of values
+ + We now catch many more kinds of "Useless use of X in sink context"
+ + A number of convenient Unicode equivalents were introduced
+ + Superscripts can now be used for integer powers
+ + Non-digit unicode characters with a numeric value (½ and such) can now be
+   used for that numeric value
+ + There is a new "approximately equal" operator
+ + Add support for USAGE argument help
+ + Provide tau constant (also: τ)
+ + Can now use channels with supply/react/whenever
+ + Bool is now a proper enum
+ + Supply/Supplier improvements
+ + Use of EVAL now requires a declaration of 'use MONKEY-SEE-NO-EVAL'
+ + Make pack and unpack experimental
+ + Dynamic variables are now visible inside start { ... } blocks
+ + Autoincrements on native ints are now faster than on Int
+ + The ~~ operator can now chain with other comparisons in many circumstances
+ + Various numeric operations now return overflow/underflow failures instead
+   of wrong value
+ + The :ss, :ii, and :mm options to s/// now all work together
 
-These are only some of the changes in this release. For a more
+This is only a partial list of the changes in this release. For a more
 detailed list, see “docs/ChangeLog”.
 
 The development team thanks all of our contributors and sponsors for