Update troubleshooting steps (#57)

src/intro/hello-world.md

@@ -248,6 +248,7 @@ that should solve the most common problems.
   - The paths must also be relative to the directory that `project.godot` is in.  Typically it'll be `res://../rust/...`.
 - Have you written the Rust code necessary to generate the entry point symbol?
   - See [above](#rust-entry-point) for how.
+- Are your gdext and Godot versions compatible? See [this page][versioning] for how to select the correct versions.
 - Is your directory structure like this below?  It's much easier when you ask for help if it is.
 
 ```txt
@@ -491,6 +492,7 @@ That's it for the _Hello World_ tutorial! The following chapters will go into mo
 [tutorial-full-script]: https://docs.godotengine.org/en/stable/getting_started/step_by_step/scripting_first_script.html#complete-script
 [gd-ignore]: https://docs.godotengine.org/en/stable/tutorials/best_practices/project_organization.html#ignoring-specific-folders
 [directory-setup]: https://godot-rust.github.io/book/intro/hello-world.html#directory-setup
+[versioning]: https://godot-rust.github.io/book/toolchain/godot-version.html
 [wikipedia-ffi]: https://en.wikipedia.org/wiki/Foreign_function_interface
 [gdextension-reloadable]: https://github.com/godotengine/godot/pull/80284
 [godot-command-line]: https://docs.godotengine.org/en/stable/tutorials/editor/command_line_tutorial.html