feature request: pull image at load instead of full refresh interval

[markfrancisonly]

It appears that the refreshable-picture-card loads with an empty image when configured to pull a camera entity image. expected behavior is refresh of the image on document appearance and cessation of refresh when no longer in view. e.g.

        var hidden, visibilityChange;
        if (typeof document.hidden !== "undefined") { // Opera 12.10 and Firefox 18 and later support
            hidden = "hidden";
            visibilityChange = "visibilitychange";
        } else if (typeof document.msHidden !== "undefined") {
            hidden = "msHidden";
            visibilityChange = "msvisibilitychange";
        } else if (typeof document.webkitHidden !== "undefined") {
            hidden = "webkitHidden";
            visibilityChange = "webkitvisibilitychange";
        }

        document.addEventListener(visibilityChange, () => {
            if (!document[hidden] ) {
                this.refreshNow();
            } else {
                this.stopRefreshLoop();
            }
        }, false);