poetry-new: add page

[girdharagrawalbro]

Adds documentation for poetry new command.

Examples included:

• Create new project with default structure
• Create new project with src layout
• Create project with specific name
• Create project without tests
• Create project with custom readme

#18042

[dmmqz]

The src layout is the default, and I don't see this flag in the documentation.

Suggested change

	- Create a new project with a source layout (src/ directory):
	`poetry new {{project_name}} --src`