Add checks for direct buffer, texture, attachment support

[greggman]

Firefox and Chrome have supported this for 3-4 months or more. Safari started supporting it in 2025-12 as of Tahoe 26.2. We're planning to switch the samples to use this new more convenient method but want to be able to tell users on older browsers to update their browsers.

[greggman]

I snuck this into quitIfWebGPUNotAvailable. I get that's a little fishy.

I could

1. leave it as is
2. rename it to quitIfWebGPUNotAvailableOrMissingFeatures
3. add a 2nd call quitIfWebGPUMissingFeatures and make every sample call it.
4. not put it here and only put it in src/main.ts
5. ?

I worry that checking in each sample will lead other devs to check. I think we'd prefer they don't check and just use this new way and tell users to upgrade. Otherwise, these checks will likely propagate for years.

[kainino0x]

lgtm, I prefer option 2 (just rename)

[greggman]

renamed