Add migration checks

[softworkz]

Closes#946

[Copilot]

Pull request overview

This PR adds automatic build-time migration validation checks to help users migrating from previous versions of Electron.NET avoid common configuration issues. The checks detect deprecated files and incorrect configurations, providing helpful guidance through MSBuild warnings.

Key Changes

• Implements 5 migration check targets that validate project configuration (package.json location, manifest files, electron-builder.json placement, parent path references, and publish profiles)
• Integrates migration checks into the build process via MSBuild targets
• Adds comprehensive documentation explaining each check and how to resolve issues

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
src/ElectronNET/build/ElectronNET.MigrationChecks.targets	New MSBuild targets file implementing 5 validation checks (ELECTRON001-006) that run before build to detect migration issues
src/ElectronNET/build/ElectronNET.Core.targets	Imports the migration checks targets file to enable automatic validation
docs/Core/Migration-Checks.md	New comprehensive documentation page explaining each migration check, why it matters, and how to fix detected issues
docs/_Sidebar.md	Adds link to Migration Checks documentation in the sidebar navigation

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

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[FlorianRappl]

LGTM - thanks!