Interpolate viscous velocity (#941)

* add function

* revise

* add docs

* add tests

* fix typo

* fix

* revise

* fix gpu tests

* revise docs

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Co-authored-by: LasNikas <[email protected]>

Author: LasNikas

src/TrixiParticles.jl

@@ -15,7 +15,7 @@ using ForwardDiff: ForwardDiff
 using GPUArraysCore: AbstractGPUArray
 using JSON: JSON
 using KernelAbstractions: KernelAbstractions, @kernel, @index
-using LinearAlgebra: norm, dot, I, tr, inv, pinv, det
+using LinearAlgebra: norm, normalize, cross, dot, I, tr, inv, pinv, det
 using MuladdMacro: @muladd
 using Polyester: Polyester, @batch
 using Printf: @printf, @sprintf