Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/templates/unsupported_browser.js

@@ -0,0 +1,38 @@
+function onHover(element, prefix) {
+    element.className += " container-hover";
+    var unHoverElement = element.querySelector('.' + prefix + ':not(.hidden)');
+    var hoverElement = element.querySelector('.' + prefix + '-hover.hidden');
+    if (unHoverElement && hoverElement) {
+        unHoverElement.className += " hidden";
+        hoverElement.className = hoverElement.className.replace(/\bhidden\b/g, "");
+    }
+}
+function onUnHover(element, prefix) {
+    element.className = element.className.replace(/\bcontainer-hover\b/g, "");
+    var unHoverElement = element.querySelector('.' + prefix + '.hidden');
+    var hoverElement = element.querySelector('.' + prefix + '-hover:not(.hidden)');
+    if (unHoverElement && hoverElement) {
+        hoverElement.className += " hidden";
+        unHoverElement.className = unHoverElement.className.replace(/\bhidden\b/g, "");
+    }
+}
+
+document.addEventListener('DOMContentLoaded', function () {
+    var hovers = document.querySelectorAll("div[data-mattermost-hover]");
+    for (var i = 0; i < hovers.length; i++) {
+        var element = hovers[i];
+        element.addEventListener("mouseover", function(e) {
+            onHover(e.currentTarget, e.currentTarget.getAttribute("data-mattermost-hover"));
+        });
+        element.addEventListener("mouseout", function(e) {
+            onUnHover(e.currentTarget, e.currentTarget.getAttribute("data-mattermost-hover"))
+        });
+    }
+    var clicks = document.querySelectorAll("div[data-mattermost-click], button[data-mattermost-click]");
+    for (var i = 0; i < clicks.length; i++) {
+        var element = clicks[i];
+        element.addEventListener("click", function(e) {
+            window.open(e.currentTarget.getAttribute('data-mattermost-click'), '_blank');
+        });
+    };
+});