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/login-page/auth/social-link-button/social-link-button.tsx

@@ -0,0 +1,47 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import type { PropsWithChildren } from 'react'
+import React from 'react'
+import { ForkAwesomeIcon } from '../../../common/fork-awesome/fork-awesome-icon'
+import type { IconName } from '../../../common/fork-awesome/types'
+import styles from './social-link-button.module.scss'
+
+export interface SocialButtonProps {
+  backgroundClass: string
+  href: string
+  icon: IconName
+  title?: string
+}
+
+/**
+ * Renders a link for a social login.
+ *
+ * @param title The link title
+ * @param backgroundClass Additional classes for the a-tag
+ * @param href The link
+ * @param icon The icon to be used
+ * @param children The children to be rendered in addition to the icon.
+ */
+export const SocialLinkButton: React.FC<PropsWithChildren<SocialButtonProps>> = ({
+  title,
+  backgroundClass,
+  href,
+  icon,
+  children
+}) => {
+  return (
+    <a
+      href={href}
+      title={title}
+      className={`btn ${styles['social-link-button']} p-0 d-inline-flex align-items-stretch ${backgroundClass}`}>
+      <span className={`${styles['icon-part']} d-flex align-items-center`}>
+        <ForkAwesomeIcon icon={icon} className={'social-icon'} fixedWidth={true} />
+      </span>
+      <span className={`${styles['text-part']} d-flex align-items-center mx-auto`}>{children}</span>
+    </a>
+  )
+}