Minor changes

tts.py

@@ -1,6 +1,6 @@
 """
 Text-to-speech synthesis (TTS) by using the FastSpeech2 model from fairseq S^2.
-This Python script convers an input text file in output wav file. The project
+This Python script converts an input text file in output wav file. The project
 was inspired by Dr. Tristan Behrens's arxiv-reader, which converts arXiv papers
 to audio. More details about the models and further examples are in the
 following sources. ↓
@@ -58,6 +58,7 @@ def main():
         line = line.replace("5G",   "5 G")
         line = line.replace("CO2",  "C O 2")
         line = line.replace("EUR",  "Euro")
+        line = line.replace("USD",  "U S Dollars")
         line = line.replace("II",   "2")
         line = line.replace("IBM",  "I B M")
         line = line.replace("IMF",  "I M F")