Improve Documentation: Add Comprehensive Import Guidance

Description

Closes #5753

Problem
Users reported confusion when working with documentation examples, particularly:

• Not knowing where range(), getYear(), and getMonth() functions come from
• Missing import statements in example code
• Having to search through the git repository to find the correct imports

Changes

1. Updated README.md

Added a new "Working with Examples" section that provides:

• Common date-fns imports needed for date manipulation (getYear, getMonth, addDays, subDays, etc.)
• Two options for the range() utility function (lodash or custom implementation)
• TypeScript type imports (ReactDatePickerCustomHeaderProps)
• Link to comprehensive imports guide

2. Created Comprehensive Imports Guide (docs/imports-guide.md)

A complete reference document including:

• Basic Setup: Required imports for every implementation
• Date Manipulation: Common date-fns functions with usage examples
• Utility Functions: range() function implementation options
• TypeScript Types: Available type exports and their usage
• Localization: How to import and register locales
• Custom Components: CalendarContainer examples
• Complete Example: Full working code with all necessary imports
• Quick Reference Table: At-a-glance import guide

Screenshots

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To reviewers

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Contribution checklist

• I have followed the contributing guidelines.
• I have added sufficient test coverage for my changes.
• I have formatted my code with Prettier and checked for linting issues with ESLint for code readability.