Congrats to the Boa team! It's great to see an independent open source project thrive and become more widely useful. This is huge impact.
On the integration with Kiesel and Chrome, I'm pleased to see that engines/browsers can share the cost of developing new language features.
Temporal is massive! Almost as big as the delta of introducing ES6. There are 4,000+ tests. The functionality does not need to be engine-specific, so it makes sense to leverage reuse.
I believe this is the first introduction of Rust into V8 itself. Which seems like a happy side-effect that hopefully makes it easier to share more Rust libraries in future. This helps keep browser development sustainable.