Add mu, m, k prefixes for Newtons

[archermarx]

In my field (spacecraft propulsion), we regularly express thrusts in terms of micro-, milli-, and kilo- Newtons. This PR adds those prefixes.

[github-actions]

Benchmark Results

	main	7c895bc...	main/7c895bc7e9fdac...
Quantity/creation/Quantity(x)	3.1 ± 0.01 ns	3.11 ± 0.01 ns	1
Quantity/creation/Quantity(x, length=y)	3.73 ± 0.01 ns	3.73 ± 0.01 ns	1
Quantity/with_numbers/*real	3.72 ± 0.91 ns	2.79 ± 0.001 ns	1.33
Quantity/with_numbers/^int	8.37 ± 1.9 ns	8.37 ± 1.9 ns	1
Quantity/with_numbers/^int * real	8.68 ± 1.6 ns	8.67 ± 1.6 ns	1
Quantity/with_quantity/+y	4.35 ± 0 ns	4.35 ± 0.01 ns	1
Quantity/with_quantity//y	3.42 ± 0.01 ns	3.42 ± 0.01 ns	1
Quantity/with_self/dimension	3.11 ± 0.01 ns	3.11 ± 0 ns	1
Quantity/with_self/inv	3.11 ± 0 ns	3.11 ± 0.001 ns	1
Quantity/with_self/ustrip	3.1 ± 0.01 ns	3.1 ± 0.01 ns	1
QuantityArray/broadcasting/multi_array_of_quantities	0.0847 ± 0.00044 ms	0.0847 ± 0.00055 ms	1
QuantityArray/broadcasting/multi_normal_array	0.0498 ± 0.00024 ms	0.0497 ± 0.00024 ms	1
QuantityArray/broadcasting/multi_quantity_array	0.0533 ± 0.0092 ms	0.0622 ± 0.00021 ms	0.857
QuantityArray/broadcasting/x^2_array_of_quantities	20 ± 3.7 μs	13.8 ± 1.5 μs	1.46
QuantityArray/broadcasting/x^2_normal_array	2.81 ± 1.9 μs	2.15 ± 0.69 μs	1.3
QuantityArray/broadcasting/x^2_quantity_array	3.64 ± 0.44 μs	3.64 ± 0.46 μs	1
QuantityArray/broadcasting/x^4_array_of_quantities	0.0814 ± 0.0005 ms	0.0815 ± 0.00038 ms	0.999
QuantityArray/broadcasting/x^4_normal_array	0.0466 ± 0.00014 ms	0.0466 ± 0.00021 ms	1
QuantityArray/broadcasting/x^4_quantity_array	0.0468 ± 0.00018 ms	0.0485 ± 0.0031 ms	0.965
time_to_load	0.192 ± 0.0019 s	0.191 ± 0.0014 s	1

Benchmark Plots

A plot of the benchmark results have been uploaded as an artifact to the workflow run for this PR.
Go to "Actions"->"Benchmark a pull request"->[the most recent run]->"Artifacts" (at the bottom).

[MilesCranmer]

Thanks!