Update de.json

i18n-web-browser-note translated from en.json, overwriting older, less complete German.
Update de.json, section i18n-web-browser-addons-note

Important: https://www.torproject.org/docs/faq.html.en#TBBJavaScriptEnabled seems to have replaced https://www.torproject.org/docs/faq.html.en#CanIBlockJS
Please correct in en.json as well, I'll stick to de.json for now.

Rather new to GitHub ;-)
merge