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>

frontend/src/components/markdown-renderer/slideshow-markdown-renderer.tsx

@@ -0,0 +1,74 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import React, { useEffect, useMemo, useRef } from 'react'
+import { useConvertMarkdownToReactDom } from './hooks/use-convert-markdown-to-react-dom'
+import { useExtractFirstHeadline } from './hooks/use-extract-first-headline'
+import { REVEAL_STATUS, useReveal } from './hooks/use-reveal'
+import type { ScrollProps } from '../editor-page/synced-scroll/scroll-props'
+import type { CommonMarkdownRendererProps } from './common-markdown-renderer-props'
+import { LoadingSlide } from './loading-slide'
+import { useMarkdownExtensions } from './hooks/use-markdown-extensions'
+import type { SlideOptions } from '../../redux/note-details/types/slide-show-options'
+import { RevealMarkdownExtension } from './extensions/reveal/reveal-markdown-extension'
+
+export interface SlideshowMarkdownRendererProps extends CommonMarkdownRendererProps {
+  slideOptions?: SlideOptions
+}
+
+/**
+ * Renders the note as a reveal.js presentation.
+ *
+ * @param className Additional class names directly given to the div
+ * @param markdownContentLines The markdown lines
+ * @param onFirstHeadingChange The callback to call if the first heading changes.
+ * @param onLineMarkerPositionChanged The callback to call with changed {@link LineMarkers}
+ * @param onTaskCheckedChange The callback to call if a task is checked or unchecked.
+ * @param onTocChange The callback to call if the toc changes.
+ * @param baseUrl The base url of the renderer
+ * @param onImageClick The callback to call if a image is clicked
+ * @param newlinesAreBreaks If newlines are rendered as breaks or not
+ * @param slideOptions The {@link SlideOptions} to use
+ */
+export const SlideshowMarkdownRenderer: React.FC<SlideshowMarkdownRendererProps & ScrollProps> = ({
+  className,
+  markdownContentLines,
+  onFirstHeadingChange,
+  baseUrl,
+  newlinesAreBreaks,
+  slideOptions
+}) => {
+  const markdownBodyRef = useRef<HTMLDivElement>(null)
+
+  const extensions = useMarkdownExtensions(
+    baseUrl,
+    undefined,
+    useMemo(() => [new RevealMarkdownExtension()], [])
+  )
+
+  const markdownReactDom = useConvertMarkdownToReactDom(markdownContentLines, extensions, newlinesAreBreaks, true)
+  const revealStatus = useReveal(markdownContentLines, slideOptions)
+
+  const extractFirstHeadline = useExtractFirstHeadline(markdownBodyRef, onFirstHeadingChange)
+  useEffect(() => {
+    if (revealStatus === REVEAL_STATUS.INITIALISED) {
+      extractFirstHeadline()
+    }
+  }, [extractFirstHeadline, markdownContentLines, revealStatus])
+
+  const slideShowDOM = useMemo(
+    () => (revealStatus === REVEAL_STATUS.INITIALISED ? markdownReactDom : <LoadingSlide />),
+    [markdownReactDom, revealStatus]
+  )
+
+  return (
+    <div className={'reveal'}>
+      <div ref={markdownBodyRef} className={`${className ?? ''} slides`}>
+        {slideShowDOM}
+      </div>
+    </div>
+  )
+}