Fix: lock docusaurus beta version,

rename back button function (planning#404)

package.json

@@ -11,8 +11,8 @@
     "write-heading-ids": "docusaurus write-heading-ids"
   },
   "dependencies": {
-    "@docusaurus/core": "^2.0.0-beta.21",
-    "@docusaurus/preset-classic": "^2.0.0-beta.21",
+    "@docusaurus/core": "2.0.0-beta.21",
+    "@docusaurus/preset-classic": "2.0.0-beta.21",
     "@mdx-js/react": "^1.6.21",
     "@svgr/webpack": "^6.2.1",
     "clsx": "^1.1.1",

static/js/custom.js

 window.addEventListener("load", function() {
-    // checks URL to see if "back to root" caret should be visible
-    const checkCaretVisibility = () => {
-        const caret = document.getElementsByClassName('fitko-navbar-icon--back')[0];
-        if (window.location.pathname === '/' && !caret.classList.contains('hidden')) {
-            caret.classList.add('hidden');
-        } else if (window.location.pathname !== '/' && caret.classList.contains('hidden')) {
-            caret.classList.remove('hidden');
+    // checks URL to see if "back to root" button should be visible
+    const checkBackBtnVisibility = () => {
+        const btn = document.getElementsByClassName('fitko-navbar-icon--back')[0];
+        if (window.location.pathname === '/' && !btn.classList.contains('hidden')) {
+            btn.classList.add('hidden');
+        } else if (window.location.pathname !== '/' && btn.classList.contains('hidden')) {
+            btn.classList.remove('hidden');
         }
     };
 
-    this.setInterval(checkCaretVisibility, 100);
+    this.setInterval(checkBackBtnVisibility, 200);
 });