allow EWW to upload files ending in newline

[ozzloy]

EWW has a bug where files uploaded ending in newline have the final
newline chomped.

I have fixed the bug and submitted a patch.  I would be greatful if
an expert on gnus and/or eww could review the patch attached to the
following message.

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=63941#50

also viewable in browser here

https://git.sr.ht/~ozzloy/emacs/commit/emacs-29-bug-63941

Thanks!