0.21.1

Changelog

f2b8abd #112 corrected checking for changes in tax rate update
5e73720 Fix channel optional name causing null pointer exception
657ecb6 Integrate GitHub Actions
90239a2 Merge pull request #111 from commercetools/doc/fix-custom-type-md
3a0c925 Merge pull request #113 from lbacz/bugfix/not-woking-tax-rate-amount
feebd27 doc: fixed linting and element_type issues