Support distributed actor

https://github.com/apple/swift-evolution/blob/main/proposals/0336-distributed-actor-isolation.md

Author: taku0

swift-mode-font-lock.el

@@ -543,7 +543,7 @@ Return nil otherwise."
   '("associatedtype" "class" "deinit" "enum" "extension" "fileprivate" "func"
     "import" "init" "inout" "internal" "let" "open" "operator" "private"
     "protocol" "public" "any" "some" "static" "struct" "subscript" "typealias"
-    "var" "actor" "nonisolated" "isolated")
+    "var" "actor" "nonisolated" "isolated" "distributed")
   "Keywords used in declarations.")
 
 (defconst swift-mode:statement-keywords

swift-mode-lexer.el

@@ -484,7 +484,8 @@ Return nil otherwise."
               '("indirect" "convenience" "dynamic" "final" "infix" "lazy"
                 "mutating" "nonmutating" "optional" "override" "postfix"
                 "prefix" "required" "static" "unowned" "weak" "internal"
-                "private" "public" "open" "fileprivate" "nonisolated"))
+                "private" "public" "open" "fileprivate" "nonisolated"
+                "distributed"))
       nil)
 
      ;; internal(set) private(set) public(set) open(set) fileprivate(set)
@@ -517,7 +518,8 @@ Return nil otherwise."
               '("indirect" "convenience" "dynamic" "final" "infix" "lazy"
                 "mutating" "nonmutating" "optional" "override" "postfix"
                 "prefix" "required" "static" "unowned" "weak" "internal"
-                "private" "public" "open" "fileprivate" "nonisolated"))
+                "private" "public" "open" "fileprivate" "nonisolated"
+                "distributed"))
       t)
 
      ;; Inserts implicit semicolon around keywords that forms single keyword

test/swift-files/indent/declarations.swift

@@ -627,6 +627,28 @@ fileprivate
       func foo()
 }
 
+@A
+distributed
+  actor
+  Foo {
+    distributed
+      func
+      foo() {
+    }
+
+    distributed
+      func
+      foo() {
+    }
+
+    distributed
+      var
+      foo
+      :
+      Int {
+    }
+}
+
 
 // Protocol declarations