docs: Add REUSE compliance status badge

Signed-off-by: Andy Scherzinger <[email protected]>

README.md

@@ -3,13 +3,14 @@
    - SPDX-FileCopyrightText: 2014-2016 ownCloud, Inc.
    - SPDX-License-Identifier: AGPL-3.0-only
 -->
-files_pdfviewer
-======
+# PDF viewer for Nextcloud
+
+[![REUSE status](https://api.reuse.software/badge/github.com/nextcloud/files_pdfviewer)](https://api.reuse.software/info/github.com/nextcloud/files_pdfviewer)
 
 This application integrates the [PDF.js](https://mozilla.github.io/pdf.js/) library into Nextcloud's Viewer.
 You can view PDF files as well as Adobe Illustrator files (.ai)
 
-![PDF Logo](https://user-images.githubusercontent.com/59488153/189176433-2f6d97a1-b151-4099-84f4-d1446a007b8a.png)
+![PDF viewer](https://user-images.githubusercontent.com/59488153/189176433-2f6d97a1-b151-4099-84f4-d1446a007b8a.png)
 
 ### Enable Javascript execution in PDF files