Add spanish translation

[mdolr]

Hello, The extension needs translation for different languages.

You can find the language code (or locale code) you should use on this page

Steps :

• Create a _locales/[language_code] folder
• Create a messages.json file at _locales/[language_code]/messages.json
• Copy paste content from _locales/en/messages.json
• Translate the "message" part for each JSON object

[EntwistleOx]

hi, i want to contribute with spanish translation