Add callout about metadata-files

(cherry picked from commit bfa32c3)

Author: cwickham

docs/projects/profiles.qmd

@@ -88,6 +88,12 @@ project:
   output-dir: _site-advanced
 ```
 
+::: {.callout-warning}
+## `metadata-files` are not resolved in profiles
+
+Instead of using `metadata-files` in a profile configuration, copy the contents of your metadata file directly into the profile configuration file.
+:::
+
 It's important to note that multiple profiles can be active. So the following enables you to vary configuration based on both `advanced` and `production` profiles:
 
 ``` {.yaml filename="_quarto.yml"}