Did you notice the </> icon for preformatted text when writing text/replying to a thread? Paste your docker-compose.yml content into the editor (make sure to have an empty line between your last written line and the pasted content, mark the content and click on the </> icon to set the marked text to “preformatted text”.
Without seeing the indention of your real files, it is way harder to figure out what the issue might be.