I had to recheck this was indeed an article from 2023, because this part surprised me greatly. To my understanding, es2016 only added Array.prototype.includes, the exponentiation operator (**), and preventing generator functions from being constructed. Even the slowest adopters already had these in 2017. Is the author assuming IE11 support?
The OP recommends to additionally package src/*.ts along with sourceMaps and declarationMaps.
What's actually the best practice here?
Some, but not all of these, are transpilable/polyfillable (refer to compat-table).
Edit: Those numbers are weighted by global usage.
[1] https://caniuse.com/?feats=mdn-javascript_builtins_array_at,...
Most modern browsers are evergreen, so targeting es2022 would be fine for most users. The exception is Safari, which is slower to incorporate new features and doesn't roll out its updates nearly as quickly as Chromium-based or Firefox, but even they have had es2016 support since 2016.
You can then use that to make your own decisions; if you're working on a high-tech video streaming platform for kids you can probably safely ignore the 5%, but if you're providing information on behalf of the government you might need to support much more than that.