README.md: minimize scope of opened file in examples

Prompted-by: Joao Rodrigo Windisch Olenscki

README.md

@@ -161,7 +161,6 @@ The package can also be used as a library:
 
 	# convert all files ending in .jpg inside a directory
 	dirname = "/path/to/images"
-	with open("name.pdf","wb") as f:
 	imgs = []
 	for fname in os.listdir(dirname):
 		if not fname.endswith(".jpg"):
@@ -170,17 +169,18 @@ The package can also be used as a library:
 		if os.path.isdir(path):
 			continue
 		imgs.append(path)
+	with open("name.pdf","wb") as f:
 		f.write(img2pdf.convert(imgs))
 
 	# convert all files ending in .jpg in a directory and its subdirectories
 	dirname = "/path/to/images"
-	with open("name.pdf","wb") as f:
 	imgs = []
 	for r, _, f in os.walk(dirname):
 		for fname in f:
 			if not fname.endswith(".jpg"):
 				continue
 			imgs.append(os.path.join(r, fname))
+	with open("name.pdf","wb") as f:
 		f.write(img2pdf.convert(imgs))