2.21.0

What's Changed

• [Scheduled] dart pub upgrade && dart pub upgrade --major-versions by @sensuikan1973 in #197
• [Scheduled] dart pub upgrade && dart pub upgrade --major-versions by @sensuikan1973 in #198
• [Scheduled] dart pub upgrade && dart pub upgrade --major-versions by @sensuikan1973 in #199
• [Scheduled] dart pub upgrade && dart pub upgrade --major-versions by @sensuikan1973 in #200
• [Scheduled] dart pub upgrade && dart pub upgrade --major-versions by @sensuikan1973 in #201
• Prepare for new Release 2.21.0 by @sensuikan1973 in #202

Full Changelog: 2.20.0...2.21.0