Add basic support for swf files in preview web app

[donmor]

Describe the solution you'd like

Swf files can be placed in a <embed> tag, as it was in past years. If either ruffle or Adobe flash player is installed, it'll be loaded into the player at the place of tag. Otherwise, some tips about flash player and a link to ruffle shows up. Useful with flash game collection... Nostalgic.

[AlexAndBear]

Embedding swf files is basically a security nightmare when it's come down to possible XSS attacks.
Wouldn't recommend it.