Merge pull request #625 from mozilla/PictureInPicture

Picture in picture

diff --cc README.md
Simple merge

diff --cc windows/de-DE/firefox.adml
Simple merge

diff --cc windows/en-US/firefox.adml
Simple merge

diff --cc windows/es-ES/firefox.adml
Simple merge

diff --cc windows/firefox.admx
Simple merge

diff --cc windows/fr-FR/firefox.adml
Simple merge

diff --cc windows/it-IT/firefox.adml
Simple merge

diff --cc windows/zh-TW/firefox.adml
Simple merge