modified get_stop_words(), preventing being changed from outside. (#31)

Co-authored-by: David Miró <davidmirom@hotmail.com>

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Co-authored-by: Alireza Savand <alireza.savand@gmail.com>
Co-authored-by: David Miró <davidmirom@hotmail.com>

Author: 3 people

stop_words/__init__.py

@@ -58,7 +58,7 @@ def get_stop_words(language, cache=True):
     if cache:
         STOP_WORDS_CACHE[language] = stop_words
 
-    return stop_words
+    return stop_words[:]    # copy list, prevent being modified
 
 _filters = {None: []}