Fan-Art gettext update and layout fix; ES svg

I added 2 'by' strings to gettext https://www.peppercarrot.com/fr/fan-art/fan-comics.html

I fixed layout for the polish translation of 'by' https://www.peppercarrot.com/pl/fan-art/fan-fiction.html
Slovene is now using the same form, as it works better with the line-breaking layout.

Added Spanish title SVG, based on webcomics#159 (closed)

Once more I report that the website code didn't update.
E.g. Asturian is still 'untranslated' https://www.peppercarrot.com/at/