slim: add page, docker-slim: convert to alias

[Managor]

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: #

[tldr-bot]

Hello! I've noticed something unusual when checking this PR at commit
1c140a9e54fb759b9b6f0d41b2ae2056c7a15bf1:

• The page pages/common/slim.md seems to be a copy of pages/common/docker-slim.md (61% matching).

Is this intended? If so, just ignore this comment. Otherwise, please double-check the commits.