Rename variables and function

[roydbt]

Is your feature request related to a problem? Please describe.
Right now, nothing happens when I select a variable and click on the refactor button.

Describe the solution you'd like
What I would like to do is to be able to rename the variable.

Describe alternatives you've considered
Just manually rename it for every occurrence.

[adam-fowler]

This is something that sourcekit-lsp has to support and support has been added and will be available in Swift 6. See swiftlang/sourcekit-lsp#498