DOC: write guide for how to replace append

[MarcoGorelli]

Pandas version checks

• I have checked that the issue still exists on the latest versions of the docs on main here

Location of the documentation

Probably as examples in concat?

Documentation problem

There are some common use-cases for append, and it's not obvious to newcomers how to use concat instead

Suggested fix for documentation

Include some examples of replacing common use-cases of append, such as #35407 (comment)

[martinbrose]

take

[EwoutH]

Thanks for creating this issue, I would love some more examples how to replace (complex) cases of append!

[anetakahle]

@MarcoGorelli I've added concat<->append examples in #47061
could you take a look please?