Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.15.7 to 3.15.8.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.15.7...v3.15.8)

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Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.15.6 to 3.15.7.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.15.6...v3.15.7)

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Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.15.5 to 3.15.6.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.15.5...v3.15.6)

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Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.15.0 to 3.15.2.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.15.0...v3.15.2)

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Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.13.0 to 3.15.0.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.13.0...v3.15.0)

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- Mark optional fields as nullable
- Add `JsonHelper`

- Shadowsocks:          some fundamental stuff
- Shadowsocks.Net:      networking & cryptography library
- Shadowsocks.PAC:      garbage
- Shadowsocks.Protobuf: geosite + geoip parsing
- Shadowsocks.WPF:      WPF GUI