templateManager: allow using regular document files as templates

As Collabora Online does not support creating templates, allow the user
to reuse documents created with richdocuments as templates.

Collabora Online supports thoe as templates.

Fixes: #5277

Author: meven

lib/TemplateManager.php

@@ -506,7 +506,9 @@ public function getEmptyFileContent(string $extension): string {
 	public function isSupportedTemplateSource(string $extension): bool {
 		$supportedExtensions = [
 			'ott', 'otg', 'otp', 'ots',
+			'odt', 'odg', 'odp', 'ods',
 			'dotx', 'xltx', 'potx',
+			'docx', 'xlsx', 'pptx',
 			'dot', 'xlt', 'pot',
 		];
 		return in_array($extension, $supportedExtensions, true);