docs: make note of the path restriction on subdir()
It's mentioned in the error message if you try to do it, that you cannot
use `..`, but it is probably useful to mention this in the online docs
too.
@@ -14,7 +14,10 @@ description: |
posargs:
dir_name:
type: str
- description: Directory relative to the current `meson.build` to enter.
+ description: |
+ Directory relative to the current `meson.build` to enter.
+
+ Cannot contain `..`
kwargs:
if_found:
