Sync .gitignore and extensions.json across repos

[sdwheeler]

PR Summary

Sync .gitignore and extensions.json across repos

• Fixes AB#544749

PR Checklist

• Descriptive Title: This PR's title is a synopsis of the changes it proposes.
• Summary: This PR's summary describes the scope and intent of the change.
• Contributor's Guide: I have read the contributors guide.
• Style: This PR adheres to the style guide.

[learn-build-service-prod]

PoliCheck Scan Report

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[learn-build-service-prod]

Learn Build status updates of commit dc0ccf1:

✅ Validation status: passed

File	Status	Preview URL	Details
.gitignore	✅Succeeded
.vscode/extensions.json	✅Succeeded

For more details, please refer to the build report.

[Copilot]

Pull request overview

This PR synchronizes configuration files (.gitignore and extensions.json) across repositories to maintain consistency. The changes expand ignored files/directories and update VS Code extension recommendations.

Changes:

• Added 4 new VS Code extensions and removed 1 extension from recommendations
• Expanded .gitignore with additional entries for build artifacts, temporary files, and platform-specific files

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 1 comment.

File	Description
.vscode/extensions.json	Added vale, gremlins, markdown-yaml-preamble, and errorlens extensions; removed markdown-pdf extension
.gitignore	Reorganized and expanded ignore patterns to include additional build artifacts, temporary files, and development-related directories

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[Copilot]

The extensions list is not in alphabetical order. The list should be sorted alphabetically by extension ID for better maintainability. For example, 'bierner.markdown-yaml-preamble' should come before 'chrischinchilla.vale-vscode', and 'chrischinchilla.vale-vscode' should come before 'docsmsft.docs-authoring-pack'.

Suggested change

	"docsmsft.docs-authoring-pack",
	"marvhen.reflow-markdown",
	"chrischinchilla.vale-vscode",
	"ms-vscode.powershell",
	"nhoizey.gremlins",
	"shuworks.vscode-table-formatter",
	"bierner.markdown-yaml-preamble",
	"bierner.markdown-yaml-preamble",
	"chrischinchilla.vale-vscode",
	"docsmsft.docs-authoring-pack",
	"marvhen.reflow-markdown",
	"ms-vscode.powershell",
	"nhoizey.gremlins",
	"shuworks.vscode-table-formatter",