Add Vector4.multiply()

[marcofugaro]

Related issue: https://discord.com/channels/685241246557667386/685241247233081362/797517091993419796

Description

This PR adds the Vector4.multiply() method.

Any reason in particular this wasn't there?

[WestLangley]

Any reason in particular this wasn't there?

See #19495

[marcofugaro]

See #19495

Wasn't aware of that discussion. It makes sense to me to keep it simple as proposed in #19495 (comment). The PR should be ok now.

[WestLangley]

@marcofugaro Can you please describe your use case? (Or modify your original post.)

[marcofugaro]

@WestLangley there was a discussion about this on discord, where a user wondered why it's not there:

[gsimone]

Chiming in, of course this can be solved in a number of way, but since the other ops are in, I don't see why multiply shouldn't, it's not much maintenance surface to add or documentation 🤷‍♂️

In my case I was trying to make something similar to shadertoy's mouse uniform, which is a v4 with x and y being used for initial POS and z w for final POS. Wanting to add axis invert, I tried multiplying by v4(invertX, invertY, invertX, invertY) and of course it doesn't work.

Ran around the issue by manually setting an m4, but that's a bit weird since I'm then applying the m4 to the v4 and yeah, it gets weird.

I want to keep the chaining style because it's way easier to read when reviewing, compact and maintainable than anything else

[mrdoob]

Thanks!