adding .txt and .rtf files support (#20)

internal/app/api/office.go

@@ -8,6 +8,8 @@ import (
 )
 
 var officeExts = []string{
+	".txt",
+	".rtf",
 	".doc",
 	".docx",
 	".odt",

internal/pkg/printer/office_test.go

@@ -20,6 +20,8 @@ func TestOffice(t *testing.T) {
 		Context: ctx,
 		FilePaths: []string{
 			fmt.Sprintf("%s/%s", dirPath, "document.docx"),
+			fmt.Sprintf("%s/%s", dirPath, "document.txt"),
+			fmt.Sprintf("%s/%s", dirPath, "document.rtf"),
 		},
 	}
 	dst := fmt.Sprintf("%s/%s", dirPath, "foo.pdf")