Add typo offsers

A sharp eye of the @musvaage spotted it in
zenodo/zenodo#2470 .
And indeed github search gives 460 hits ATM
https://github.com/search?q=offsers&type=code
and they look like legit typos.

Typo is really close to offser->offset one, but upon
quick github search I never found offser to be a typo
for offer. I think that spurious "s" in offsers is mechanical,
and thus I did not bother adding second variant for "offser" typo
to be offer

codespell_lib/data/dictionary.txt

@@ -37686,6 +37686,7 @@ offsence->offence
 offsense->offense
 offsenses->offenses
 offser->offset
+offsers->offers
 offsest->offsets, offset,
 offseted->offsetted
 offseting->offsetting