-----Description-----
This task requires writing a Lean 4 function that converts a binary number represented as a list of digits (0 or 1) into its corresponding decimal value. The list is ordered in big-endian format, meaning the most significant digit comes first.
The function should interpret the list as a binary number and return its decimal representation as a natural number.

-----Input-----
The input is a list of natural numbers:
digits: A list of digits, each of which is either 0 or 1, representing a binary number in big-endian order.

-----Output-----
The output is a natural number:
Returns the decimal value of the binary number represented by the input list.

