Finish Spanish translation + small fixes

[jorgesumle]

#18

[jorgesumle]

By the way, which version of Hugo is used to generate the site? Using hugo v0.148.1 I get the following warning and no text shows up:

WARN  Skip unknown config key "about"
WARN  Skip unknown config key "contact"
WARN  Skip unknown config key "download"
WARN  Skip unknown config key "footer"
WARN  Skip unknown config key "hero"
WARN  Skip unknown config key "navigation"

A way to fix this is doing a change like this:

-  [Languages.en.hero]
+  [Languages.en.params.hero]