add_languages.py may need fixing

[jwestw]

I had multiple issues when trying to run add_languages.py.

• It didn't consistently create the pages in _pages,
• didn't consistently change the yaml, to add the permalink and the language.
• it created pages in _posts, but didn't change the name of the file
• it didn't change the yaml in the posts either.

Also, I suggest better documentation for users to create more languages when not using the site starter.

[brockfanning]

@jwestw I just tried it and noticed that it was leaving in the old language in the yaml. So it was ending up with both language: en and the new language as well. I've just pushed a fix for that problem.

Also, technically it's not necessary to change the name of files - though I see that the Spanish example does have a different name. To avoid that confusion I've just renamed the Spanish example post to be the same name as the English one.

With these changes do you still see any inconsistencies in the yaml changes?

I agree we should add more detail on this process and I've got a more detailed step-by-step in one of the tutorials in this PR: open-sdg/open-sdg#805