Add filter for formatting dollar values

tests/test_filters.py

@@ -0,0 +1,15 @@
+import pytest
+
+from atst.filters import dollars
+
+
+@pytest.mark.parametrize("input,expected", [
+    ('0', '$0'),
+    ('123.00', '$123'),
+    ('1234567', '$1,234,567'),
+    ('-1234', '$-1,234'),
+    ('one', '$0'),
+])
+def test_dollar_fomatter(input, expected):
+    assert dollars(input) == expected
+