Warn about config limits for scripts

Author: philderbeast

doc/scripts.md

@@ -14,6 +14,16 @@ is most often `stack script` but it can be, for example, `stack runghc`. If
 there is no Stack interpreter options comment, Stack will warn that one was
 expected.
 
+!!! warn
+
+   No project-level configuration is available for scripts and scripts will
+   ignore any supplied `--stack-yaml=<project-level-config-file>. As some
+   settings don't have a command line equivalent and can only be set via YAML,
+   such as `extra-deps`, `allow-newer` and `allow-newer-deps`, if a script would
+   need these options to build then your only choice is to edit the global
+   configuration or to limit package dependencies of scripts to those included
+   with a given resolver.
+   
 An example will be easiest to understand. Consider the Haskell source file
 `turtle-example.hs` with contents: