Rule Request: swiftui_private_var_func `private vars` before `var body`

New Issue Checklist

• Updated SwiftLint to the latest version
• I searched for existing GitHub issues

New rule request

1. This rule should be added to help with coding conventions so that all variables are before the body of a SwiftUI View..

Triggers

struct ListView: View {
   var body: some View {
   }

   private var title: String {
     "My Title
   }
}

Won't trigger

struct ListView: View {
   private var title: String {
     "My Title
   }

   var body: some View {
   }
}

3. I can't think of any configuration rules.
4. This rule should be opt-in

To be honest, I'd be happy to just create a custom rule for this, but I'm not sure how that could be achieved, maybe someone could give me a few tips, like what match_kinds I'd need if it were possible ?

Start by reviewing SwiftLint's existing opt-in rules and how custom rules use match_kinds. Compare the requested trigger and non-trigger examples with existing rule tests, then define coverage for SwiftUI View declarations and private variables. Done means the rule enforces variables before var body, remains opt-in, and has tests for both examples.