enh(swift) add actor keyword (#3171)

* (swift) add `actor` keyword

Coming in Swift 5.5, per [Swift Evolution](https://github.com/apple/swift-evolution/blob/main/proposals/0306-actors.md)

* (swift) add markup tests for all type constructors

These appeared to be missing before, so are now tested to be keywords.

* (swift) treat 'actor' similarly to 'class' and others

* (swift) move type definition tests to seperate suite

* (swift) fix type definition tests

* (swift) remove trailing line from type definition test case

* (swift) add extension and protocol to type definition test suite

CHANGES.md

@@ -57,6 +57,7 @@ Parser:
 
 Grammars:
 
+- enh(swift) add `actor` keyword (#3171) [Bradley Mackey][]
 - enh(crystal) highlight variables (#3154) [Josh Goebel][]
 - fix(ruby) Heredoc without interpolation (#3154) [Josh Goebel][]
 - enh(swift) add `@resultBuilder` attribute (#3151) [Bradley Mackey][]

src/languages/lib/kws_swift.js

@@ -32,6 +32,7 @@ export const keywords = [
   // strings below will be fed into the regular `keywords` engine while regex
   // will result in additional modes being created to scan for those keywords to
   // avoid conflicts with other rules
+  'actor',
   'associatedtype',
   'async',
   'await',

src/languages/swift.js

@@ -471,7 +471,7 @@ export default function(hljs) {
       FUNCTION,
       INIT_SUBSCRIPT,
       {
-        beginKeywords: 'struct protocol class extension enum',
+        beginKeywords: 'struct protocol class extension enum actor',
         end: '\\{',
         excludeEnd: true,
         keywords: KEYWORDS,

test/markup/swift/type-definition.expect.txt

@@ -0,0 +1,6 @@
+<span class="hljs-keyword">class</span> <span class="hljs-title class_">TestClass</span> {}
+<span class="hljs-keyword">struct</span> <span class="hljs-title class_">TestStruct</span> {}
+<span class="hljs-keyword">enum</span> <span class="hljs-title class_">TestEnum</span> {}
+<span class="hljs-keyword">actor</span> <span class="hljs-title class_">TestActor</span> {}
+<span class="hljs-keyword">extension</span> <span class="hljs-title class_">TestExtension</span> {}
+<span class="hljs-keyword">protocol</span> <span class="hljs-title class_">TestProtocol</span> {}

test/markup/swift/type-definition.txt

@@ -0,0 +1,6 @@
+class TestClass {}
+struct TestStruct {}
+enum TestEnum {}
+actor TestActor {}
+extension TestExtension {}
+protocol TestProtocol {}