fix: Move content into to frontend directory

Doing this BEFORE the merge prevents a lot of merge conflicts.

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

src/components/intro-page/intro-custom-content.tsx

@@ -1,40 +0,0 @@
-/*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
- *
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-import React, { useEffect } from 'react'
-import { RenderIframe } from '../editor-page/renderer-pane/render-iframe'
-import { RendererType } from '../render-page/window-post-message-communicator/rendering-message'
-import { fetchFrontPageContent } from './requests'
-import { Logger } from '../../utils/logger'
-import { useAsync } from 'react-use'
-import { AsyncLoadingBoundary } from '../common/async-loading-boundary'
-
-const logger = new Logger('Intro Content')
-
-/**
- * Fetches the content for the customizable part of the intro page and renders it.
- */
-export const IntroCustomContent: React.FC = () => {
-  const { value, error, loading } = useAsync(async () => (await fetchFrontPageContent()).split('\n'), [])
-
-  useEffect(() => {
-    if (error) {
-      logger.error('Error while loading custom intro content', error)
-    }
-  }, [error])
-
-  return (
-    <AsyncLoadingBoundary loading={loading} error={error} componentName={'custom intro content'}>
-      <RenderIframe
-        frameClasses={'w-100 overflow-y-hidden'}
-        markdownContentLines={value as string[]}
-        rendererType={RendererType.INTRO}
-        forcedDarkMode={true}
-        adaptFrameHeightToContent={true}
-      />
-    </AsyncLoadingBoundary>
-  )
-}