Drift 2.20.1

This patch release fixes the following issues:

Core drift package

• Migrate legacy package:drift/web.dart to the new JS interop SDK libraries. For backwards compatibility, the channel() extension on the MessagePort class in dart:html has been kept.
  Once dart:html is removed from the Dart SDK, that extension will have to be removed from drift as well.
• Fix cast errors in the protocol for remote workers when compiling with dart2wasm.
• Introduce a faster protocol for communicating with workers. This protocol is enabled automatically after upgrading drift_worker.js.

Generator

• Strip leading numbers when generating modular accessor names for drift files, fixing syntax errors.
• Support triggers targeting views.
• Include dialect-specific constraints in exported schema files.
• Fix schema export not respecting column constraints of the target dialect.
• Resolve json_extract return types from context if possible.