Add note to "help translate" page

[WorldLanguages]

Adds a small note to the page. See diff

Reminder: also update TurboWarp's page accordingly.

[WorldLanguages]

Also: should change "48 hours" to "96 hours"

[Hans5958]

Also, while we're at it, can we remove line 60 and update line 13 to something like this?

Thanks for the interest to help with translating Scratch Addons to other languages! Scratch Addons is available in more than 15 languages thanks to the help of volunteers around the world.

Please read this page carefully to continue.

[WorldLanguages]

@Hans5958 Sure, go ahead and change it.

[WorldLanguages]

@Hans5958 Done

[Hans5958]

You may merge at your own discretion, or I will do it tommorow.