Add CHANGELOG.md entries for 0.20.0 to 0.20.5 (#3842)
Add CHANGELOG.md entries for 0.20.0 to 0.20.5 (#3842)


timifasubaa/incubator-superset,timifasubaa/incubator-superset,airbnb/superset,mistercrunch/panoramix,mistercrunch/panoramix,apache/incubator-superset,alanmcruickshank/superset-dev,apache/incubator-superset,zhouyao1994/incubator-superset,dmigo/incubator-superset,airbnb/superset,airbnb/caravel,alanmcruickshank/superset-dev,airbnb/superset,mistercrunch/panoramix,airbnb/caravel,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,airbnb/caravel,apache/incubator-superset,timifasubaa/incubator-superset,dmigo/incubator-superset,dmigo/incubator-superset,zhouyao1994/incubator-superset,timifasubaa/incubator-superset,apache/incubator-superset,zhouyao1994/incubator-superset,apache/incubator-superset,alanmcruickshank/superset-dev,airbnb/caravel,dmigo/incubator-superset,alanmcruickshank/superset-dev,mistercrunch/panoramix,airbnb/superset