mysql: add zh translation

[witt-bit]

• [✔] 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):

[CLAassistant]

All committers have signed the CLA.

[tldr-bot]

Hello! I've noticed something unusual when checking this PR:

• The page pages.zh/common/mysql.md has a more info link that does not match the one in the English page. Please check the "More information:" translation as well using https://github.com/tldr-pages/tldr/blob/main/contributing-guides/translation-templates/more-info-link.md.

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

[spageektti]

Hi. Could you please translate the placeholders too?