add gdshader tests

tests/query/highlights/gdshader/test.gdshader

@@ -0,0 +1,26 @@
+shader_type spatial;
+
+render_mode unshaded, wireframe;
+// <- @keyword
+//          ^^^^^^^^ @keyword
+//                    ^^^^^^^^^ @keyword
+
+/** My Doc comment*/
+//^^^^^^^^^^^^^^^^^^ @comment.documentation
+uniform float MY_VALUE: interesting_hint = 1.0;
+//<- @keyword 
+//      ^^^^^ type.builtin
+//            ^^^^^^^^ constant
+//                    ^ @punctuation.delimiter
+//                      ^^^^^^^^^^^^^^^^ @attribute
+//                                       ^ @operator
+//                                         ^^^ @number.float
+//                                            ^ punctuation.delimiter
+
+void vertex() {
+// <- type.builtin
+//   ^^^^^^ @function
+  do {} while (123< 2231);
+//^^ keyword.repeat
+//      ^^^^^ keyword.repeat
+}