Add shader textureBias

[slimbuck]

This PR:

• adds a global textureBias uniform to control biased texture reads across standard material textures
• enables WEBGL_depth_texture extension on webgl1 devices (used when creating texture-based render targets)
• updates example package-lock file to version 2

These changes aid with the implementation of a high quality, multi-frame rendering solution.

Questions:

1. the biased version of texture2D is supported out-of-the-box on webgl 1.0, but is there any overhead calling this version of the function when bias is 0? (I expect probably not, but how do we check?)

Answers:

1. likely no performance impact

[willeastcott]

we don't want GrabPass to become official public API yet: do we flag the class as @private or @ignore?

Use @ignore.

@private is just for class fields and methods and not classes themselves.

[willeastcott]

Did you mean to update pacakge-lock.json in this PR?

[slimbuck]

Did you mean to update pacakge-lock.json in this PR?

Yes! but forgot to add to the PR description.

[willeastcott]

Awesome. Maybe edit the PR title tho.

[mvaligursky]

related to #2856

[mvaligursky]

I think we should have a public API for this. Ideally the viewer code you test it on would not do
this.scope.resolve("textureBias").SetValue(...);

[willeastcott]

This transform feedback example already uses this API. This uniform management is long overdue a redesign.

[mvaligursky]

That's true, but transform feedback example is accessing this API to set uniforms in its own shader.
But here we're adding new functionality to the engine that the Viewer wants to use .. and that should be different API, allowing us to even rename the variable later if needed. Maybe `Scene.standardMaterialTextureBias' or a shorter version of it? Something we publicly document.

[willeastcott]

I'd prefer something like Scene#textureBias and then potentially add Texture#bias which would take precedence.

[slimbuck]

Could be a scene setting... though I would prefer creating and exposing public API in followup PR.

[willeastcott]

Fine by me.