feat(standalone): export async transform - #17653

The compilers of repl-sdk use two things from Babel: the
`transform-typescript` plugin and the `react` preset. `@babel/standalone`
has every plugin and preset, the unicode tables for regex transforms
(641 kB), and the data of preset-env.

`packages/babel-8-lite` is a private package, not published. It bundles
`@babel/core` 8 with only those two parts into one browser-ready file,
in the shape of `@babel/standalone`. Its own build replaces what Babel 8
needs from node: `node:path`, `node:assert` (Babel calls only
`assert()` and `assert.fail()`), and the `process` global. So the
packages that bundle it need no configuration for it.

ember-repl has it as a dev dependency, so rollup bundles it as its own
chunk. The build of ember-repl stays on Babel 7, and ember-repl needs
no `@babel/core` peer. In the repl app the Babel chunk goes from
2796 kB to 1143 kB, and from 453 kB to 241 kB compressed.

The import map key is `@glimdown/babel-8-lite`, because this is not
`@babel/standalone`. repl-sdk asks for that name. A host that does not
provide it gets `@babel/standalone@8` from esm.sh, which has the same
API.

`transform` is `transformSync`, as in `@babel/standalone`. In
`@babel/core` 8, `transform` needs a callback, and the react compiler
calls it synchronously.

The tarball existed for `transformAsync` (babel/babel#17653), which is
in Babel 8. The root package and the browser tests of repl-sdk now use
`@babel/standalone` 8 from npm.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>