Write up a guide on how to edit/make translations for NavPay

[navtrello]

Things to detail:

• software needed (po file editor, gitkraken for pulling repo/making branches)
• how to make a github acc
• how to fork our repo
• how to make a branch
• how to use the po editing software
• how to add a language to the UI options
• how to create a PR

We may not want them to edit the UI since that's rather technical for a lot of people, especially on top of all the github stuff. We can always add the language to the UI ourselves.