[wasm] ship a single isomorphic npm package from the wasm crate

[turbocrime]

the wasm crate's npm packaging script currently builds multiple targets, and publishes each target as a separate package to npm.

the completely separate wasm-ts package in the web monorepo pulls in both packages as dependencies, resulting in a duplicated 90MB dependency.

these targets differ primarily in js bindings. it is possible to package an isomorphic binding. other projects have successfully shipped target-agnostic wasm packages.

rustwasm/wasm-pack#1334

package size should improve after #2712 breaks out a large binary blob, but this should still be addressed.