gui: Introduce PreviewGeneratorOdt for basic previews of .odt files

gui/previewgenerator.cpp

@@ -2,13 +2,15 @@
 #include "previewgenerator.h"
 #include "previewgeneratorpdf.h"
 #include "previewgeneratorplaintext.h"
+#include "previewgeneratorodt.h"
 
 static PreviewGenerator *plainTextGenerator = new PreviewGeneratorPlainText();
 
 static QMap<QString, PreviewGenerator *> generators{
 	{"pdf", new PreviewGeneratorPdf()}, {"txt", plainTextGenerator},  {"md", plainTextGenerator},
 	{"py", plainTextGenerator},			{"java", plainTextGenerator}, {"js", plainTextGenerator},
-	{"cpp", plainTextGenerator},		{"c", plainTextGenerator},	  {"sql", plainTextGenerator}};
+	{"cpp", plainTextGenerator},		{"c", plainTextGenerator},	  {"sql", plainTextGenerator},
+	{"odt", new PreviewGeneratorOdt()}};
 
 PreviewGenerator *PreviewGenerator::get(QFileInfo &info)
 {