Fix Normalize transform

[raghavmecheri]

Describe the bug
I've hardcoded this entire function call -- it's specific to a 3-dimensional array, where the innermost element has 3 channels. This is probably not a good idea at all.

To Reproduce
There's no bug at the moment, so this is redundant. I'm sure this'll lead to a load of different bugs if not fixed though.

Expected behavior

• Generalises to different sized input arrays
• Maybe something more efficient than 3 nested loops?

Screenshots
N/A

Desktop (please complete the following information):
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Additional context
Ref:

pytorchjs/src/torchvision/transforms/transforms.js

Line 48 in 4611105

_norm = (arr, mean, std) => {