putty: add page

[jhauga]

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.

[CLAassistant]

All committers have signed the CLA.

[Managor]

You'll need to sign the CLA or we won't be able to merge this.

[znarfm]

Move the page in common/ as it is also available for linux and osx, regardless of being mostly used in Windows.

[znarfm]

Thank you for your contribution!

[ivanbaluta]

Thank you for contribution!