Moved main.js out of global folder

Signed-off-by: Jim Martens <github@2martens.de>

_assets/javascripts/main.js

@@ -0,0 +1,41 @@
+"use strict";
+
+//= require popper.js/dist/popper
+//= require echo-js/dist/echo
+//= require bootstrap/js/dist/util
+//= require bootstrap/js/dist/collapse
+//= require bootstrap/js/dist/tooltip
+
+$(function() {
+    let mainMenu = $("#mainmenuNavbar");
+    mainMenu.on("show.bs.collapse", function () {
+        $("#submenuNavbar").addClass("invisible");
+    });
+    mainMenu.on("hidden.bs.collapse", function () {
+        $("#submenuNavbar").removeClass("invisible");
+    });
+
+    let backToTop = $("#back-to-top");
+    $(window).scroll(function () {
+        if ($(this).scrollTop() > 50) {
+            backToTop.fadeIn();
+        } else {
+            backToTop.fadeOut();
+        }
+    });
+    backToTop.click(function () {
+        backToTop.tooltip("hide");
+        $("body,html").animate({
+            scrollTop: 0
+        }, 800);
+        return false;
+    });
+
+    backToTop.tooltip();
+
+    echo.init({
+        offset: 500,
+        throttle: 250,
+        unload: false
+    });
+});