Fixes # 146 Added onkeydown trap of shift-tab/tab on first and last elements in settings to keep focus in dialog until closed.
Fixes # 146
Added onkeydown trap of shift-tab/tab on first and last elements
in settings to keep focus in dialog until closed.

cene-co-za/readium-js-viewer,readium/readium-js-viewer,GermanCentralLibraryForTheBlind/readium-js-viewer,AndyHubert/readium-js-viewer,GermanCentralLibraryForTheBlind/readium-js-viewer,looknear/readium-js-viewer,kivuto/readium-js-viewer,becka11y/readium-js-viewer,joemerante/readium-js-viewer-firefox,becka11y/readium-js-viewer,cene-co-za/readium-js-viewer,readium/readium-js-viewer,NYULibraries/readium-js-viewer,mrmayfield/readium,AndyHubert/readium-js-viewer,NYULibraries/readium-js-viewer,kivuto/readium-js-viewer,mrmayfield/readium,looknear/readium-js-viewer