feat: add swift indents (#4756)

tests/indent/swift/declarations.swift

@@ -0,0 +1,51 @@
+@wrapper
+@modifier(
+  *
+)
+class EquilateralTriangle: NamedShape {
+  var sideLength: Double = 0.0
+
+  @attr
+  init(
+    sideLength: Double, 
+    name: String
+  ) {
+    self.sideLength = sideLength
+  }
+
+  var perimeter: Double {
+    willSet {
+    }
+  }
+
+  @funcattr
+  override func simpleDescription(a: int, b: int) -> String {
+    return "An equilateral triangle with sides of length \(sideLength)."
+  }
+}
+
+@attr
+protocol ExampleProtocol {
+  var simpleDescription: String { get }
+  mutating func adjust()
+}
+
+@available(*)
+func test() {
+
+}
+
+@attr(*)
+typealias Foo = Bar
+
+@attr
+struct Foo<
+  Bar
+> {
+  @Provider
+  var test = 1
+
+  subscript(index: Int) -> Int {
+    var foo = 2
+  }
+}