docs: add README with installation and usage documentation

[Copilot]

README contained only the module title — no guidance on prerequisites, installation, or how to run the module.

Changes

• Prerequisites — PowerShell 7.1+, Microsoft.Graph SDK install command, required Entra ID permissions (LifecycleWorkflows.Read.All / LifecycleWorkflows.ReadWrite.All)
• Installation — PowerShell Gallery (Install-Module) and from-source (git clone + Import-Module) paths
• Usage — step-by-step connect → run flow, plus a full end-to-end example:

Connect-MgGraph -Scopes 'LifecycleWorkflows.Read.All'
Invoke-LCWMermaidGenerator -ReportPath './LifecycleWorkflowsReport.md'

• Parameter reference — table for -ReportPath (type, required, default, description)
• Output description — explains console output and the generated Markdown report, including the color-coded Mermaid diagram node legend

Original prompt

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This section details on the original issue you should resolve

<issue_title>Missing readme with documentation on how to run</issue_title>
<issue_description>Missing readme with documentation on how to run</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Missing readme with documentation on how to run #4

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.