blkid: add page

[newtant]

• The page (if new), does not already exist in the repo.
• The page is in the correct platform directory (common/, linux/, etc.)
• The page has 8 or fewer examples.
• The PR title conforms to the recommended templates.
• The page follows the content guidelines.

First pull request, I think I adhered to the guidelines/rules, but feel free to tell me if either the page itself or the pull request could need some improvement.

[tldr-bot]

The build for this PR has failed with the following error(s):

pages/linux/blkid.md:3: TLDR004 Command descriptions should end in a period
pages/linux/blkid.md:1: TLDR009 Page should contain a newline at end of file

Please fix the error(s) and push again.

[sbrl]

Thanks, @newtant 😺