Ruby 3.0.0 RC1 Released

- RBS is a language to describe the types of Ruby programs.

- TypeProf is a type analysis tool bundled in the Ruby package.

- Ractor is an Actor-model like concurrent abstraction designed to provide a parallel execution feature without thread-safety concerns.

- Fiber#scheduler is introduced for intercepting blocking operations. This allows for light-weight concurrency without changing existing code.

- One-line pattern matching is redesigned. (experimental)

- Endless method definition is added.

- Memory view is added as an experimental feature

- Performance improvements(MJIT)