chore(packaging): bump version to 2.0.0-alpha.21; add changelog

chore(packaging): bump version to 2.0.0-alpha.20

chore(packaging): bump version to 2.0.0-alpha.19

chore(release): bump version to 2.0.0-alpha.18

For docs

chore(release): bump version

Somehow the version bump from alpha.16 was not submitted to master…

bump version to 2.0.0-alpha.16

chore: bump up the version to 2.0.0-alpha.15

chore(packaging): bump version to alpha.14

release 2.0.0-alpha.13 on npm/pub