Raise tsconfig default to ES2015 or later

[NagayamaToshiaki]

Acknowledgement

• I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion.

Comment

According to CanIUse, more than 96% of the current brousers used have ES2015 support.
As of ES2022, nine out of ten browsers are ready to use the feature.
Why do you stick to 15-year-old ES5 as default?

[MartinJohns]

Related: #10117 / #47572. Possible candidate for #54500.