In Fly launch config page > build section > dockerfile, put the gotch…

…as with this setup in a callout.

reference/configuration.html.markerb

@@ -109,7 +109,10 @@ The image builder is used when you want to immediately deploy an existing public
 
 `dockerfile` accepts a relative path to a Dockerfile, or a URL. By default, `flyctl` looks for `Dockerfile` in the application root.
 
-**Gotchas:** 1) This option will not change the Docker context path, which is set to the project root directory by default. If you want the `Dockerfile` to use its containing directory as the context root, use `fly deploy <directory>`. 2) When specifying a local Dockerfile, make sure it's not excluded from the Docker build context in your `.dockerignore`.
+<div class="callout">
+- This option will not change the Docker context path, which is set to the project root directory by default. If you want the `Dockerfile` to use its containing directory as the context root, use `fly deploy <directory>`.
+- When specifying a local Dockerfile, make sure it's not excluded from the Docker build context in your `.dockerignore`.
+</div>
 
 ### Specify a Docker ignore file