fix(a11y): WCAG 2.1 AA fixes (#2219)

apps/client/src/features/editor/components/table-of-contents/table-of-contents.tsx

@@ -3,7 +3,7 @@ import { TextSelection } from "@tiptap/pm/state";
 import React, { FC, useEffect, useRef, useState } from "react";
 import classes from "./table-of-contents.module.css";
 import clsx from "clsx";
-import { Box, Text } from "@mantine/core";
+import { Box, Text, Title } from "@mantine/core";
 import { useTranslation } from "react-i18next";
 
 type TableOfContentsProps = {
@@ -156,9 +156,9 @@ export const TableOfContents: FC<TableOfContentsProps> = (props) => {
   return (
     <>
       {props.isShare && (
-        <Text mb="md" fw={500}>
+        <Title order={2} size="h6" mb="md" fw={500}>
           {t("Table of contents")}
-        </Text>
+        </Title>
       )}
       <div className={props.isShare ? classes.leftBorder : ""}>
         {links.map((item, idx) => (