docs: 🐛 css enhancement + add gtag

Signed-off-by: slumbering <slumbering.pierrot@gmail.com>

website/src/theme/Heading/index.js

@@ -0,0 +1,52 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/* eslint-disable jsx-a11y/anchor-has-content, jsx-a11y/anchor-is-valid */
+import React from 'react';
+import clsx from 'clsx';
+import {translate} from '@docusaurus/Translate';
+import {useThemeConfig} from '@docusaurus/theme-common';
+import './styles.css';
+import styles from './styles.module.css';
+import AnchorIcon from "./anchor.svg"
+
+const Heading = (Tag) =>
+  function TargetComponent({id, ...props}) {
+    const {
+      navbar: {hideOnScroll},
+    } = useThemeConfig();
+
+    if (!id) {
+      return <Tag {...props} />;
+    }
+
+    return (
+      <Tag {...props}>
+        <a
+          aria-hidden="true"
+          tabIndex={-1}
+          className={clsx('anchor', {
+            [styles.enhancedAnchor]: !hideOnScroll,
+          })}
+          id={id}
+        />
+        {props.children}
+        <a
+          className="hash-link"
+          href={`#${id}`}
+          title={translate({
+            id: 'theme.common.headingLinkTitle',
+            message: 'Direct link to heading',
+            description: 'Title for link to heading',
+          })}>
+          <AnchorIcon />
+        </a>
+      </Tag>
+    );
+  };
+
+export default Heading;

website/src/theme/Heading/styles.css

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+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+.anchor {
+  display: block;
+  position: relative;
+  top: -0.5rem;
+}
+
+.hash-link {
+  opacity: 0;
+  padding-left: 0.5rem;
+  transition: opacity var(--ifm-transition-fast);
+}
+
+.hash-link:focus,
+*:hover > .hash-link {
+  opacity: 1;
+}

website/src/theme/Heading/styles.module.css

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+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+.enhancedAnchor {
+  top: calc(var(--ifm-navbar-height) * -1 - 0.5rem);
+}