add pic document type

frontend/document/picdocument.lua

@@ -0,0 +1,26 @@
+
+PicDocument = Document:new{
+	_document = false,
+	dc_null = DrawContext.new(),
+}
+
+function PicDocument:init()
+	ok, self._document = pcall(pic.openDocument, self.file)
+	if not ok then
+		self.error_message = "failed to open jpeg image"
+		return
+	end
+
+	self.info.has_pages = true
+	self.info.configurable = false
+
+	self:readMetadata()
+end
+
+function PicDocument:readMetadata()
+	self.info.number_of_pages = 1
+end
+
+
+DocumentRegistry:addProvider("jpeg", "application/jpeg", PicDocument)
+DocumentRegistry:addProvider("jpg", "application/jpeg", PicDocument)