add rust usage example

test_rust.py

@@ -0,0 +1,11 @@
+from pathlib import Path
+from thermaldecoder import decode
+import numpy as np
+import matplotlib.pyplot as plt
+root = Path('frames')
+root.mkdir(exist_ok=True)
+frames = decode('in.pcap', 'frames')
+f = np.array(frames[0])
+f.shape = (384, 288)
+plt.imshow(f)
+plt.show()