BUG: Missing documentation for read_spss()

[isantolin]

Problem description

New added feature read_spss() #26537 doesn´t still have any kind of documentation about it http://pandas-docs.github.io/pandas-docs-travis/user_guide/io.html

[TomAugspurger]

We'll want to add

1. an entry in the table in user_guide/io.rst
2. A small doc section in user_guide/io.rst explaining things
3. API docs in reference/io.rst

[another-green]

I'll take this task.