backwward(s)->backward(s), onwward(s)->onward(s)

I spotted "onwwards" in the field.  "forwward->forwward" etc. were
already present.

Author: cjwatson

codespell_lib/data/dictionary.txt

@@ -8996,6 +8996,8 @@ backwarks->backwards
 backwars->backward, backwards,
 backwrad->backward
 backwrads->backwards
+backwward->backward
+backwwards->backwards
 bacome->become, became,
 bacomes->becomes
 bacoming->becoming
@@ -41538,6 +41540,8 @@ onwer->owner
 onwership->ownership
 onwing->owning
 onws->owns
+onwward->onward
+onwwards->onwards
 ony->only, on, one,
 onyl->only
 oommits->commits