[Review] Arno 2

[mborland]

The introduction is very confusing, I have no idea if/when I should use this versus boost multi versus std. Two solutions: design a clear decision graph, or come up with a summary table that compares features absent/present across the main competitors. He kinda tried to it in a written form, but the result is so abstract my brain refuses to parse it. In this case, small C++ expressions can help enrich the decision chart and/or comparison table:

for example

feature | this lib | std | boost multi | FancyMulti |
`someCppExpression` allocates ? | Yes | No | Yes | Yes |

[correaa]

I added this sentence to the introduction after mentioning std::mdspan: "In summary, if you need owning arrays, clear value semantics, and iterators or ranges compatibility, and you only need strided array layouts, use this library instead of std::mdspan."

There is also this table from the start: https://correaa.gitlab.io/boost-multi/multi/appendix.html#appendix_comparison