Add support for inline classes

See dart-lang/sdk#49734 and https://github.com/dart-lang/language/blob/master/accepted/future-releases/inline-classes/feature-specification.md.

Inline is only detected as part of class, the spec says:

> The token `inline` is not made a built-in identifier: the reserved word `class` that occurs right after `inline` serves to disambiguate the inline class declaration with a fixed lookahead.

Author: DanTup

grammars/dart.json

@@ -336,7 +336,7 @@
 				},
 				{
 					"name": "keyword.declaration.dart",
-					"match": "(?<!\\$)\\b(abstract|sealed|base|interface|class|enum|extends|extension|external|factory|implements|get(?!\\()|mixin|native|operator|set(?!\\()|typedef|with|covariant)\\b(?!\\$)"
+					"match": "(?<!\\$)\\b(abstract|sealed|base|interface|inline class|class|enum|extends|extension|external|factory|implements|get(?!\\()|mixin|native|operator|set(?!\\()|typedef|with|covariant)\\b(?!\\$)"
 				},
 				{
 					"name": "storage.modifier.dart",

test/goldens/inline.dart.golden

@@ -0,0 +1,53 @@
+>// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+#^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ comment.line.double-slash.dart
+>// for details. All rights reserved. Use of this source code is governed by a
+#^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ comment.line.double-slash.dart
+>// BSD-style license that can be found in the LICENSE file.
+#^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ comment.line.double-slash.dart
+>
+>inline class MyInt {
+#^^^^^^^^^^^^ keyword.declaration.dart
+#             ^^^^^ support.class.dart
+>  final int it;
+#  ^^^^^ storage.modifier.dart
+#        ^^^ support.class.dart
+#              ^ punctuation.terminator.dart
+>  MyInt(this.it);
+#  ^^^^^ support.class.dart
+#        ^^^^ variable.language.dart
+#            ^ punctuation.dot.dart
+#                ^ punctuation.terminator.dart
+>  void foo() { print('MyInt.foo'); }
+#  ^^^^ storage.type.primitive.dart
+#       ^^^ entity.name.function.dart
+#               ^^^^^ entity.name.function.dart
+#                     ^^^^^^^^^^^ string.interpolated.single.dart
+#                                 ^ punctuation.terminator.dart
+>}
+>
+>final inline = 1;
+#^^^^^ storage.modifier.dart
+#             ^ keyword.operator.assignment.dart
+#               ^ constant.numeric.dart
+#                ^ punctuation.terminator.dart
+>
+>int get inline = 1;
+#^^^ support.class.dart
+#    ^^^ keyword.declaration.dart
+#               ^ keyword.operator.assignment.dart
+#                 ^ constant.numeric.dart
+#                  ^ punctuation.terminator.dart
+>set inline(int value) {}
+#^^^ keyword.declaration.dart
+#    ^^^^^^ entity.name.function.dart
+#           ^^^ support.class.dart
+>
+>void inline() {
+#^^^^ storage.type.primitive.dart
+#     ^^^^^^ entity.name.function.dart
+>  var inline = 1;
+#  ^^^ storage.type.primitive.dart
+#             ^ keyword.operator.assignment.dart
+#               ^ constant.numeric.dart
+#                ^ punctuation.terminator.dart
+>}

test/test_files/inline.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+inline class MyInt {
+  final int it;
+  MyInt(this.it);
+  void foo() { print('MyInt.foo'); }
+}
+
+final inline = 1;
+
+int get inline = 1;
+set inline(int value) {}
+
+void inline() {
+  var inline = 1;
+}