systemctl-list-unit-files: add page

[mady20]

• The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• The page(s) have at most 8 examples.
• 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 title conforms to the recommended templates.
• Version of the command being documented (if known):

[dmmqz]

Suggested change

	`systemctl list-unit-files 'sshd*'`
	`systemctl list-unit-files '{{sshd*}}'`