Add: magnet default parser

Add: Decoder unit tests

Refactor: update err message for consistency

Refactor: update error messages in Decode

Add: out of bounds guard in Decode

Fix: digit check logic in Decode and last char skip in decodeList

Refactor: update variable names for consistency

Fix: corrected the position of error byte when EOF reached for decode list

Add: bencode dict decode logic

Fix: bencode string decode when length contains non digit chars

Refactor: bencode decoder error messages to add more context

Add: Bencode list decode logic

Add: Decode string logic

Add: decoder.go and decode int logic

Add: go.mod