Export webgl features even on non-wasm32

[jesses-canva]

We need to be able to reference these without gating our code on #[cfg(target_arch = "wasm32")].

Tested with

cargo hack check -p vello_encoding --feature-powerset
cargo hack check -p vello --feature-powerset
cargo hack check -p glifo --feature-powerset --at-least-one-of std,libm
cargo hack check -p vello_common --feature-powerset --at-least-one-of std,libm
cargo hack check -p vello_hybrid --feature-powerset --at-least-one-of std,libm
cargo hack check -p vello_cpu --feature-powerset --at-least-one-of std,libm --at-least-one-of u8_pipeline,f32_pipeline