(chore): Update contributing.md to include mobile poeditor link

Added link to translations poeditor site for mobile app

added PlatformBrowser Priority2 - Medium ProductDocs TypeChore + 1 deleted label

merged

mentioned in commit e3d96c83

The only problem here is it doesn't include mobile translations. It should really link to https://www.minds.com/localization which needs to be updated with the mobile link.