Some docs fixes

[gaurav-arya]

• Adapt to the Documenter.jl breaking release 1.0.0. This made strict checks on my default, which seems to be fine for most of the checks, except :missing_docs, which I manually excluded (that tests that every single docstring is in the public docs, which seems a bit excessive).

• Remove index.md, since it is auto-generated and the current file is outdated

[github-actions]

Benchmark Results

	main	7ce237e...	t[main]/t[7ce237e...]
Quantity/creation/Quantity(x)	3.2 ± 0.1 ns	3.2 ± 0.1 ns	1
Quantity/creation/Quantity(x, length=y)	3.7 ± 0.1 ns	3.7 ± 0.1 ns	1
Quantity/with_numbers/*real	3.2 ± 0.1 ns	3.2 ± 0.1 ns	1
Quantity/with_numbers/^int	10.1 ± 2.5 ns	10.1 ± 2.4 ns	1
Quantity/with_numbers/^int * real	10.5 ± 2.5 ns	10.5 ± 2.4 ns	1
Quantity/with_quantity/+y	5.9 ± 0.1 ns	5.9 ± 0.1 ns	1
Quantity/with_quantity//y	3.7 ± 0.1 ns	3.7 ± 0.1 ns	1
Quantity/with_self/dimension	1.6 ± 0.1 ns	1.6 ± 0.1 ns	1
Quantity/with_self/inv	3.7 ± 0.1 ns	3.7 ± 0.1 ns	1
Quantity/with_self/ustrip	1.6 ± 0.1 ns	1.6 ± 0.1 ns	1
QuantityArray/broadcasting/multi_array_of_quantities	0.193 ± 0.02 ms	0.193 ± 0.02 ms	0.999
QuantityArray/broadcasting/multi_normal_array	0.0686 ± 0.0011 ms	0.0677 ± 0.001 ms	1.01
QuantityArray/broadcasting/multi_quantity_array	0.228 ± 0.0021 ms	0.231 ± 0.0022 ms	0.987
QuantityArray/broadcasting/x^2_array_of_quantities	0.0339 ± 0.0048 ms	0.0345 ± 0.0053 ms	0.983
QuantityArray/broadcasting/x^2_normal_array	7.8 ± 1.5 μs	7.3 ± 1.8 μs	1.07
QuantityArray/broadcasting/x^2_quantity_array	9.7 ± 1.2 μs	9.8 ± 1.2 μs	0.99
QuantityArray/broadcasting/x^4_array_of_quantities	0.113 ± 0.0056 ms	0.112 ± 0.0051 ms	1.01
QuantityArray/broadcasting/x^4_normal_array	0.0579 ± 0.0011 ms	0.0577 ± 0.0009 ms	1
QuantityArray/broadcasting/x^4_quantity_array	0.085 ± 0.0041 ms	0.085 ± 0.0042 ms	1
time_to_load	0.165 ± 0.00018 s	0.166 ± 0.00076 s	0.995

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]

Nice work, LGTM!