Integrate ruffle and add adobe flash (.swf) support

[Anonyymi]

• Add ruffle as npm dependency for easy upgradability
• Bundle ruffle as an independent output javascript file with webpack
• Add support for uploading SWF-files, validate mime-type properly
• Add thumbnail for SWF-files
• Add support for expand/shrink of SWF-files
• Expand should create ruffle player and size the content same way as is done for other file types

[Anonyymi]

This is done.