[feat] Open with: choose which engine to use for file (#3653)

Fixes #3345

* Add SVG to MuPDF filetypes

frontend/document/djvudocument.lua

@@ -12,6 +12,7 @@ local DjvuDocument = Document:new{
     options = KoptOptions,
     koptinterface = nil,
     color_bb_type = Blitbuffer.TYPE_BBRGB24,
+    provider = "djvulibre",
     provider_name = "DjVu Libre",
 }