Update messages.json (zh_CN)
Update messages.json (zh_CN)

* i18n_add_items: Delete <br/>
* i18n_html_readium_tm_a_project: change the github repository reference
NYULibraries/readium-js-viewer,cene-co-za/readium-js-viewer,readium/readium-js-viewer,looknear/readium-js-viewer,AndyHubert/readium-js-viewer,GermanCentralLibraryForTheBlind/readium-js-viewer,joemerante/readium-js-viewer-firefox,looknear/readium-js-viewer,becka11y/readium-js-viewer,mrmayfield/readium,GermanCentralLibraryForTheBlind/readium-js-viewer,readium/readium-js-viewer,kivuto/readium-js-viewer,mrmayfield/readium,AndyHubert/readium-js-viewer,becka11y/readium-js-viewer,NYULibraries/readium-js-viewer,kivuto/readium-js-viewer,cene-co-za/readium-js-viewer