uuid: add comprehensive example functions for documentation

[mrbishalbaniya]

This commit adds example functions to the uuid package to improve documentation and demonstrate common usage patterns:

• Example: Basic UUID generation and parsing
• ExampleNew: Generating a new UUID
• ExampleNewV4: Version 4 (random) UUID generation
• ExampleNewV7: Version 7 (timestamp-based) UUID generation
• ExampleParse: Parsing UUIDs in various formats
• ExampleMustParse: Parsing with panic on error
• ExampleNil: The Nil UUID
• ExampleMax: The Max UUID
• ExampleUUID_String: Converting UUID to string
• ExampleUUID_Compare: Comparing UUIDs

These examples will appear in the package documentation and help users understand how to use the uuid package effectively.

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