[Tails-l10n] [review] Update on the documentation to build t…

Dear all,

the documentation to build the wiki offline within Tails was
outdated[1], please review the following draft:

http://git.tails.boum.org/elouann/tails/tree/wiki/src/contribute/build/website.mdwn?h=build-the-wiki-offline-within-tails&id=120ee6d7a5d865ce69f24a0c3cf7609c0a2fac5d

Repository: http://git.tails.boum.org/elouann/tails/
Branch: build-the-wiki-offline-within-tails

Thank you,
~ elouann

[1] https://labs.riseup.net/code/issues/9018