Candidates for FAQ

It's not yet clear whether we'll have an FAQ section in the book and if yes, how we are going to structure it. One idea would be to have 100% of the information as part of the tutorial, and use the FAQ only to refer to different chapters and sections. This way, people reading the book from A-Z would not miss anything, and we don't have to duplicate content.

This issue tracks potential candidates for often-asked questions. Once more basic parts of the book are done, we can decide what to do with these. Very basic questions such as "how can I use `Gd`" or "how do I export an enum" should **NOT** be part of the FAQ, these should be covered in the tutorial.

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## Questions, by category

### Classes and objects

- [ ] Can `init` take parameters?
- [ ] How do I get a `T` from a `Gd`?
- [ ] Can I attach Rust scripts to a node?
What do I do if one Rust class should be used by differently typed nodes in the tree?
- [ ] How do I create a singleton?
- [ ] Can I store references/lifetimes in a `GodotClass`?
- [ ] `GDExtension entry point 'gdext_rust_init' not found in library`
Typically indicates that `lib.rs` is not compiled, or the cdylib is created in a different path.

### Tooling