Implement a function to decode Bitcoin-encoded numbers.

Background

In Bitcoin, numbers are often encoded in a special format:

• Numbers are stored in little-endian format (least significant byte first).
• The most significant bit of the last byte indicates the sign (0 for positive, 1 for negative).
• For negative numbers, the absolute value is encoded, and then the result is negated.

For example:

• 0x01 represents 1
• 0x81 represents -1
• 0xff00 represents 255
• 0xff80 represents -128

Task

Complete the decodeNum function in challenges/BitcoinDecoder.js:

1. Implement the logic to decode a Bitcoin-encoded number from a Buffer.
2. Handle both positive and negative numbers correctly.
3. Return the decoded integer value.

Implementation

export function decodeNum(buffer) {
    // TODO: Implement the decoding logic here
    // Remember to handle both positive and negative numbers
    // Return the decoded integer value
}