Fortran documentation out-of -date

[hr87]

Describe the bug
The Fortran documentation is lacking descriptions for several routines. The one I found missing is adios2_attribute_data. Furthermore, it seems like the documentation for adios2_set_steps_selection is actually for the wrong method. Additionally, the description for the latter is not clear in the C++ section either.

To Reproduce

1. Go to the documentation
2. Look for adios2_attribute_data

Expected behavior
Find a clear description of method

[williamfgc]

@hr87 thanks for pointing this out. Yes, the Fortran docs are a bit of a pain to maintain since they are not automatically handled by readthedocs + breathe + doxygen (same with tests, there is currently no testing framework, but just assert style checks). It's the hassle of mixing Fortran and modern infrastructure. Fortran bindings are essentially (almost) replicating the C bindings (those are automatically handled), check the docs for adios2_set_steps_selection. Also, since adios2 relies on its community members, feel free to do a PR at anytime since all of the documentation source code resides under docs in particular Fortran full APIs.

[dmitry-ganyushin]

Documentation is updated with PR #2559