More units

[Mo-Gul]

I'd argue that mbar is also a quite common unit. At least much more than dL. And because I also think that cL is at least as common as dL that should be added as well.
Feel free to cherry-pick.

[github-actions]

Benchmark Results

	main	df86e36...	t[main]/t[df86e36...]
Quantity/creation/Quantity(x)	3.1 ± 0.01 ns	2.79 ± 0.01 ns	1.11
Quantity/creation/Quantity(x, length=y)	3.11 ± 0.01 ns	3.11 ± 0.01 ns	1
Quantity/with_numbers/*real	3.1 ± 0.01 ns	3.1 ± 0.01 ns	1
Quantity/with_numbers/^int	8.37 ± 2.5 ns	8.05 ± 2.2 ns	1.04
Quantity/with_numbers/^int * real	8.37 ± 2.5 ns	8.05 ± 2.2 ns	1.04
Quantity/with_quantity/+y	5.27 ± 0.01 ns	5.27 ± 0.01 ns	1
Quantity/with_quantity//y	3.11 ± 0.01 ns	3.41 ± 0.01 ns	0.912
Quantity/with_self/dimension	1.56 ± 0.01 ns	1.55 ± 0.01 ns	1.01
Quantity/with_self/inv	3.11 ± 0.001 ns	3.11 ± 0.01 ns	1
Quantity/with_self/ustrip	1.55 ± 0.01 ns	1.55 ± 0.01 ns	1
QuantityArray/broadcasting/multi_array_of_quantities	0.15 ± 0.013 ms	0.147 ± 0.14 ms	1.02
QuantityArray/broadcasting/multi_normal_array	0.0498 ± 0.00031 ms	0.053 ± 0.0092 ms	0.941
QuantityArray/broadcasting/multi_quantity_array	0.158 ± 0.0009 ms	0.158 ± 0.00059 ms	1
QuantityArray/broadcasting/x^2_array_of_quantities	25 ± 1.9 μs	25.1 ± 1.8 μs	0.997
QuantityArray/broadcasting/x^2_normal_array	4.29 ± 0.99 μs	4.31 ± 1 μs	0.995
QuantityArray/broadcasting/x^2_quantity_array	6.92 ± 0.23 μs	6.12 ± 0.46 μs	1.13
QuantityArray/broadcasting/x^4_array_of_quantities	0.0784 ± 0.00046 ms	0.0784 ± 0.00073 ms	1
QuantityArray/broadcasting/x^4_normal_array	0.0497 ± 0.00016 ms	0.0497 ± 0.0002 ms	1
QuantityArray/broadcasting/x^4_quantity_array	0.0592 ± 0.00017 ms	0.0594 ± 0.0061 ms	0.997
time_to_load	0.241 ± 0.0066 s	0.243 ± 0.0056 s	0.989

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!

[Mo-Gul]

I have to thank (all of) you for your awesome work !!!