{
    "manifest_version": 2,
    "name": "Capslight",
    "description": "Highlight capital words",
    "version": "1.0",
"content_scripts":
    [
        {
            "matches": ["http://*/*","https://*/*"],
            "js":["jquery.js", "myscript.js"],
            "run_at": "document_end"
        }
    ]

}

"matches": ["http://www.stackoverflow.com/*","http://www.superuser.com/*","https://google.co.uk/*"],

$('body').each(function(){
    var pattern = /([A-Z]{3,})/g;
    var before = '<span style="background: yellow;">';
    var after = '</span>';
    $(this).html($(this).html().replace(pattern, before+"$1"+after));
});