Convert source to JSR dependencies

[lukeed]

Is your feature request related to a problem? Please describe.

It's only related to the fact that, as it is, the JSR package is hardcoded to an old std version.

Describe the solution you'd like

All dependencies would point to jsr: specifiers. There'd be no need for a custom convert_to_jsr step.
And since JSR is "the way" forward for Deno packaging, this package would still remain "native" to all Deno usages.