Mark `require_one_based_indexing` and `has_offset_axes` as public

[adrhill]

The discussion here mentions require_one_based_indexing being part of the public API: https://github.com/JuliaLang/julia/pull/43263

Both functions are also documented (albeit in the dev docs):

• require_one_based_indexing: https://docs.julialang.org/en/v1/devdocs/offset-arrays/#man-custom-indices
• has_offset_axes: https://docs.julialang.org/en/v1/devdocs/offset-arrays/#For-objects-that-mimic-AbstractArray-but-are-not-subtypes

Towards https://github.com/JuliaLang/julia/issues/51335.

[giordano]

Both functions are also documented (albeit in the dev docs)

It'd be much better to have them documented outside of the devdocs though.

[adrhill]

Do you want me to include them somewhere? I'm not sure which section in docs.julialang.org/en/v1/base/arrays/ is best suited. Maybe "Array functions"?

[adrhill]

"Indexing and assignment" is probably a better fit.

[LilithHafner]

Tagging triage because this adds new API.

[LilithHafner]

Two approvals, 6 +1s on the OP and no blocking comments seems plenty to bypass triage. @mbauman, are you okay with merging this PR despite your lack of excitement?