Add l10n support

[adan89lion]

Create strings file to let contributor to make & improve localised translations. Plik can detect user's browser region or locale settings and show them localised webpage (making end-users who don't understand English a friendlier interface).

I can contribute to Korean & Chinese (Simplified and Traditional) translation in the future.

[Glandos]

Given the nice user interface, users also expect to be welcomed in their own language.

I can do the French translation, but I guess that the core team can do it also :wink:

[Ricardo-Simoes]

I can do Portuguese European (pt-PT)