Add new section on lifecycle of the block.

[dhruvikpatel18]

Closes #56276

What?

Adds a new "Lifecycle of a block" section to the "Fundamentals of Block Development" documentation to explain the different phases and transformations a block goes through.

Why?

Developers new to block development often struggle to understand:

• How blocks transition through different phases
• When and how blocks transform between different formats
• Best practices for handling lifecycle events
• The relationship between edit, save, and render phases

This documentation provides a clear overview of the block lifecycle to help developers better understand these concepts.

How?

Added a new markdown file docs/getting-started/fundamentals/lifecycle-of-block.md that:

• Details the five main phases of a block's lifecycle
• Explains block format transformations
• Provides code examples for each lifecycle phase
• Includes best practices for handling lifecycle events

Updated the main README.md to include a link to the new section.

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Co-authored-by: dhruvikpatel18 <[email protected]>
Co-authored-by: juanmaguitar <[email protected]>

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