feat: Add cell_padding configurable option

[DenverCoder1]

Adds an option to configure the amount of cell padding.

table2ascii(
    header=["#", "G", "H", "R", "S"],
    body=[[1, 2, 3, 4, 5]],
    footer=["A", "B", 1, 2, 3],
    first_col_heading=True,
    cell_padding=0,
)
"""
╔═╦═══════╗
║#║G H R S║
╟─╫───────╢
║1║2 3 4 5║
╟─╫───────╢
║A║B 1 2 3║
╚═╩═══════╝
"""

table2ascii(
    header=["#", "G", "H", "R", "S"],
    body=[[1, 2, 3, 4, 5]],
    footer=["A", "B", 1, 2, 3],
    first_col_heading=True,
    cell_padding=2,
)
"""
╔═════╦═══════════════════════╗
║  #  ║  G     H     R     S  ║
╟─────╫───────────────────────╢
║  1  ║  2     3     4     5  ║
╟─────╫───────────────────────╢
║  A  ║  B     1     2     3  ║
╚═════╩═══════════════════════╝
"""