[changelog] Update changelog for 0.15.14 release (#2638)

CHANGELOG.md

@@ -1,5 +1,19 @@
 # Changelog
 
+# 0.15.14
+
+## Features
+
+- **M3Query**: Add movingSum, movingMax, movingMin Graphite functions ([#2570](https://github.com/m3db/m3/pull/2570))
+- **M3Query**: Add aliasByTags Graphite function ([#2626](https://github.com/m3db/m3/pull/2626))
+- **M3Query**: Add exponentialMovingAverage Graphite function ([#2622](https://github.com/m3db/m3/pull/2622))
+- **M3Query**: Add timeSlice Graphite function ([#2581](https://github.com/m3db/m3/pull/2581))
+- **M3Query**: Add delay Graphite function ([#2567](https://github.com/m3db/m3/pull/2567))
+- **M3Query**: Add aggregateWithWildcards Graphite function ([#2582](https://github.com/m3db/m3/pull/2582))
+- **M3Query**: Add groupByNodes Graphite function ([#2579](https://github.com/m3db/m3/pull/2579))
+- **M3Coordinator**: Allow using the placement set API for creating new placements as well as upserting existing placements ([#2625](https://github.com/m3db/m3/pull/2625))
+- **M3DB**: Add bootstrap time migration config which supports seamless backwards and forwards compatible fileset upgrades ([#2521](https://github.com/m3db/m3/pull/2521))
+
 # 0.15.13
 
 ## Bug Fixes