TF-3450 Refactor image and text preview

core/lib/domain/preview/supported_preview_file_types.dart

@@ -3,6 +3,7 @@ class SupportedPreviewFileTypes {
     'image/bmp',
     'image/jpeg',
     'image/gif',
+    'image/webp',
     'image/png',];
 
   static const textMimeTypes = [
@@ -10,6 +11,10 @@ class SupportedPreviewFileTypes {
     'text/markdown',
   ];
 
+  static const jsonMimeTypes = [
+    'application/json',
+  ];
+
   static const docMimeTypes = [
     'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
     'application/vnd.oasis.opendocument.text',