Added sentence about our volunteer experts 🙌

Signed-off-by: Anneke Sinnema <mail@annekesinnema.nl>

Author: anneke

_includes/content/4-werkt-de-app-veilig.md

@@ -1,6 +1,6 @@
-
 Yes, the app is secure. We make sure that:
 -  The app is constantly tested.
 -  The app does not know your name or any other personal details.
 -  Nobody can force you to use the app.
 -  Experts from inside and outside the government have helped to design the app.
+-  Hundreds of volunteer experts have verified the quality, privacy and security of the app. The way the app works is completely transparent and [open source](https://minvws.github.io/nl-covid19-notification-app-community-website/).

_questions/nl/4-werkt-de-app-veilig.md

@@ -16,3 +16,4 @@ Ja, de app is veilig. Daar zorgen we voor:
 - De app kent niet jouw naam of contactgegevens.
 - Niemand mag je dwingen om de app te gebruiken.
 - Deskundigen binnen en buiten de overheid helpen mee om de app te bouwen.
+- Honderden vrijwillige experts kijken mee naar de bouwkwaliteit, privacy en veiligheid van de app. De werking van de app is helemaal transparant en [open source](https://minvws.github.io/nl-covid19-notification-app-community-website/).