Deno runtime support

Continuing from https://github.com/donmccurdy/glTF-Transform/pull/380 and #379, I intend to support Deno as an environment. The I/O class has been added, but a few remaining things to do:

- [ ] Unit test coverage: #456
- [ ] CI: #836
- [ ] Publish to https://jsr.io/

Context:

- https://github.com/avajs/ava/discussions/2743

TypeScript's magic `./foo` → `./foo.ts` resolution is causing quite a headache here.

- https://github.com/denoland/deno/issues/2506
- https://github.com/microsoft/TypeScript/issues/27481
- https://github.com/microsoft/TypeScript/issues/37582
- https://github.com/microsoft/TypeScript/pull/51669 (possible resolution?)

Start by reviewing the context from pull requests #380 and #379, then inspect the remaining work in unit test coverage (#456), CI (#836), and JSR publishing. Check the TypeScript and Deno module-resolution references in the issue. Done means Deno support has tests, CI coverage, and a package published to jsr.io.

Written by the indexing model from the issue text.