manifest.json

{
   "manifest_version" : 2,
    "name"       : "Transcription pop-up",
    "version"    : "0.1",
    "description": "Shows transcription of an English word on double click",
    "content_scripts": [{
        "matches": ["http://*/*", "file://*/*"],
        "js"     : ["trans.js"],
        "run_at" : "document_idle"
    }]
}