Document IO Error (#6712)
`IOError` is special, it is not actually a lint but an error before
linting. I'm not entirely sure how to document it since it does not
match the general lint rule pattern (`Checks that the file can be read
in its entirety.` is imho worse).
I added the in my experience two most common reasons for io errors on
unix systems and linked two tutorials on how to fix them.
See https://github.com/astral-sh/ruff/issues/2646
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Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>
