Add guide for creating reusable Material components

[Mr-KRAMA]

This PR addresses a long-standing community request for documentation on how to wrap existing Angular Material components to create reusable custom components.

Problem
Developers frequently struggle with creating custom components that wrap Material components like mat-select and mat-input while maintaining form integration, validation, and Material Design features. This has been a pain point for 4+ years (see issue #21371).

Solution
Added a comprehensive guide with practical examples showing how to:
Wrap mat-select with predefined options

Create formatted input components (phone number example)

Handle async data loading with autocomplete

Implement proper ControlValueAccessor patterns

Support form validation and accessibility

What's included
Documentation : New guide at guides/creating-reusable-material-components.md

Working examples : Permission select and phone input components

Best practices : Testing, validation, and accessibility patterns

Real-world patterns : Covers the exact scenarios developers requested

Testing
✅ Linting passes

✅ Files properly formatted

✅ Examples follow Angular Material patterns

Impact
This guide will help thousands of Angular developers who currently struggle with component composition patterns. The examples are copy-paste ready and follow official Angular standards.

Closes #21371

[crisbeto]

Closing this as another example of AI slop.