skip empty param for suffix and prefix

[v2ngu]

Added a new option for suffix and prefix wrangles to skip empty cells

      skip_empty:
        type: boolean
        desription: Whether to skip empty values
        default: (Optional) false

[cerdamario13]

Fix failing tests:

• test_suffix_skip_mult_empty_false()
• est_suffix_skip_mult_empty_true():

looks like its just a missed 'ly' on some of the strings.

Also if you want to assert multiple items in a df, you can convert df column to a list to make the code more concise

def test_prefix_skip_mult_empty_false():
    """
    Testing format.prefix with skip_empty false
    """
    data = pd.DataFrame({
        'col1': ['terrestrial','','ordinary'],
        'col2': ['soft','','cripsy'],
    })
    recipe = """
    wrangles:
        - format.prefix:
            input:
                - col1
                - col2
            output: 
                - out1
                - out2
            value: extra-
    """   
    df = wrangles.recipe.run(recipe, dataframe=data)
     assert df['out1'].tolist() == ['extra-terrestrial', 'extra-', 'extra-ordinary']
     # ... rest of assertions

Other than that, looks great!