Trigger implicit_getter even if the getter is mutating

[rraphaeldev]

In case of a mutating getter, the get keyword must be specified to add the mutating behavior but this trigger the implicit_getter warning.

struct Counter {
  private var count: Int
  
  init(start: Int = 0) {
    self.count = start
  }
  
  var next: Int? {
    mutating get { // warning: Implicit Getter Violation: Computed read-only properties should avoid using the get keyword. (implicit_getter)
      defer {
        self.count += 1
      }
      
      return self.count
    }
  }
}

Edit: swiftlint version: 0.19.0

[marcelofabri]

Similar to #1309

[marcelofabri]

Implemented in #1678.