feat: introduce Cap'n Web Adapter

[yusukebe]

The author should do the following, if applicable

• [ ] Add tests
• [ ] Run tests
• [ ] yarn changeset at the top of this repo and push the changeset
• [ ] Follow the contribution guide

[changeset-bot[bot]]

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Latest commit: 699d65986f2b242290bde2c45e24feab04e0b332

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