Update docs and add doctests

[abhro]

Please see the commmit messages for relevant changes

[github-actions]

Benchmark Results

	main	ffccc36...	main / ffccc36...
Quantity/creation/Quantity(x)	3.11 ± 0.01 ns	4.02 ± 0.011 ns	0.773
Quantity/creation/Quantity(x, length=y)	3.43 ± 0.01 ns	3.43 ± 0.01 ns	1
Quantity/with_numbers/*real	3.11 ± 0.01 ns	3.11 ± 0 ns	1
Quantity/with_numbers/^int	8.37 ± 1.6 ns	8.37 ± 1.6 ns	1
Quantity/with_numbers/^int * real	8.98 ± 1.6 ns	8.98 ± 1.6 ns	1
Quantity/with_quantity/+y	4.35 ± 0 ns	4.35 ± 0 ns	1
Quantity/with_quantity//y	3.11 ± 0.001 ns	3.11 ± 0 ns	1
Quantity/with_self/dimension	3.11 ± 0.01 ns	3.11 ± 0.01 ns	1
Quantity/with_self/inv	3.11 ± 0 ns	3.11 ± 0 ns	1
Quantity/with_self/ustrip	2.79 ± 0 ns	2.8 ± 0.92 ns	1
QuantityArray/broadcasting/multi_array_of_quantities	0.0873 ± 0.00099 ms	0.0873 ± 0.00064 ms	0.999
QuantityArray/broadcasting/multi_normal_array	0.0496 ± 0.0021 ms	0.0497 ± 0.00022 ms	0.999
QuantityArray/broadcasting/multi_quantity_array	0.053 ± 0.00016 ms	0.053 ± 0.00024 ms	1
QuantityArray/broadcasting/x^2_array_of_quantities	14.1 ± 1.8 μs	14 ± 2.1 μs	1.01
QuantityArray/broadcasting/x^2_normal_array	2.19 ± 1.1 μs	2.14 ± 0.84 μs	1.02
QuantityArray/broadcasting/x^2_quantity_array	3.47 ± 0.14 μs	3.48 ± 0.12 μs	0.997
QuantityArray/broadcasting/x^4_array_of_quantities	0.0812 ± 0.00066 ms	0.0811 ± 0.00065 ms	1
QuantityArray/broadcasting/x^4_normal_array	0.0466 ± 0.00018 ms	0.0466 ± 0.00018 ms	1
QuantityArray/broadcasting/x^4_quantity_array	0.0467 ± 0.003 ms	0.0467 ± 0.00017 ms	0.999
time_to_load	0.199 ± 0.00099 s	0.204 ± 0.0083 s	0.979

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).