admin: split monitor list in 3, add sending text selection to monitor

public/monitor.css

@@ -4,6 +4,9 @@ body {
   margin: 0px auto;
   overflow: hidden;
 }
+.hidden {
+  visibility: hidden;
+}
 .container {
   display: flex;
   width: 1280px;
@@ -68,5 +71,17 @@ iframe {
   height: 21px; /* 1 line height */
   overflow: hidden;
 }
+#text-overlay {
+  width: 720px;
+  background-color: var(--main-bg-color);
+  outline: 0.7em solid var(--main-fg-color);
+  -moz-outline-radius: 1em;
+  position: absolute;
+  top: 310;
+  left: 280px;
+  padding: 1em;
+  font-size: 1.5em;
+  text-align: center;
+}
 /*1280 x 720*/
 /*1920 x 1080*/