Add create-neuron command

[anoop2811]

This is command should create the basic neuron structure and allow it to be created in a chosen folder. If a folder is not given, create it in current folder.
Validations:

1. A name for the neuron is mandatory
2. If a neuron of the same name exists in the folder where it is creating, it should exit with exit code 1 and give an error message to the same
3. Allow a -d flag to create in the directory given. Also validate the directory exists and is writable

[mailprak]

Completed Validations
The create-neuron command now has all requested features:

✅ Mandatory name validation (line 36): Enforced by cobra.ExactArgs(1) - requires exactly one argument
✅ Default to current folder (line 53): -d flag defaults to "." if not provided
✅ -d flag support (line 53): --dir/-d flag allows specifying target directory
✅ Directory existence check (lines 58-62): Validates the directory exists before proceeding
✅ Directory writability check (lines 64-70): Creates a test file to verify write permissions
✅ Duplicate neuron detection (lines 76-80): Checks if neuron already exists and exits with code 1
✅ Absolute paths (lines 90-91): Uses absolute paths for exec_file in generated neuron.yaml