Document entity types better

[jyn514]

Consider a frontend that wants to emit a call instruction. The documentation states that you need to pass

• a FuncRef
• a slice of Values

However, neither of the documentations for those types show how you can get an instance of them! For Value you can look around on the rest of the page for InstBuilder and see that most instructions return a Value, but for FuncRef it's non-obvious that you need to either call import_function or declare_func_in_func. It would be great to link to these pages in the documentation for FuncRef.

Similar problems exist for

• GlobalValue
• Ebb
• Inst
• JumpTable
• Heap
• Table
• SigRef
• StackSlot
• Constant

[jyn514]

Does anyone know how to make a link to a dependent crate? I want to link to cranelift_module::Module in a cranelift_codegen file.