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/common/base-url/base-url-context-provider.tsx

@@ -0,0 +1,38 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import React, { createContext, useState } from 'react'
+import type { PropsWithChildren } from 'react'
+
+export interface BaseUrls {
+  renderer: string
+  editor: string
+}
+
+interface BaseUrlContextProviderProps {
+  baseUrls?: BaseUrls
+}
+
+export const baseUrlContext = createContext<BaseUrls | undefined>(undefined)
+
+/**
+ * Provides the given base urls as context content and renders an error message if no base urls have been found.
+ *
+ * @param baseUrls The base urls that should be set in the context
+ * @param children The child components that should receive the context value
+ */
+export const BaseUrlContextProvider: React.FC<PropsWithChildren<BaseUrlContextProviderProps>> = ({
+  baseUrls,
+  children
+}) => {
+  const [baseUrlState] = useState<undefined | BaseUrls>(() => baseUrls)
+
+  return baseUrlState === undefined ? (
+    <div className={'text-white'}>HedgeDoc is not configured correctly! Please check the server log.</div>
+  ) : (
+    <baseUrlContext.Provider value={baseUrlState}>{children}</baseUrlContext.Provider>
+  )
+}