sgdisk: add page

[duvvuvenkataramana]

Adds comprehensive documentation for the sgdisk command with 8 common usage examples.

Resolves #19275

Checklist

• The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• The page description(s) have links to documentation or a homepage.
• The page(s) follow the content guidelines.
• The page(s) follow the style guide.
• The PR contains at most 5 new pages.
• The PR is authored by me, or has been human-reviewed if it was created with AI or machine translation software.
• The PR title conforms to the recommended templates.
• Version of the command being documented (if known):

Reference issue: #

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[duvvuvenkataramana]

@tldr-pages/maintainers - This PR adds comprehensive documentation for the sgdisk command, resolving issue #19275. The documentation includes 8 common usage examples for GUID partition table (GPT) management. All checklist items have been verified and the contribution follows the project guidelines. Please review and merge at your convenience. Thank you!

[ivanbaluta]

#19290