Now that Node 18 is the new LTS version of Node, it should be safe to
support ES2022 features. The install docs have already been updated to
recommend Node 18.x in 41a710854e.
This will break support on Node 16.x and earlier.
Also update TypeScript to 4.9 which contains various typechecking
improvements: https://devblogs.microsoft.com/typescript/announcing-typescript-4-9/
Ref: FoundKeyGang/FoundKey#238
Changelog: Changed