add highlights tests

tests/query/highlights/hocon/test.conf

@@ -0,0 +1,59 @@
+HOCON = Human-Optimized Config Object Notation
+// ^field
+//        ^string
+//                       ^string
+//                              ^string
+//                                    ^string
+
+"it's": "a JSON\nsuperset",
+//       ^string
+//             ^string.escape
+//                        ^punctuation.delimiter
+
+features: [
+//      ^operator
+//        ^punctuation.bracket
+    less noisy / less pedantic syntax
+//             ^string
+    ability to refer to another part of the configuration
+    import/include another configuration file into the current file
+    a mapping to a flat properties list such as Java's system properties
+    ability to get values from environment variables
+    # ability to write comments
+//  ^comment
+//     ^comment
+    // this is also a comment 
+//  ^comment
+//     ^comment
+]
+
+specs url: "https://github.com/lightbend/config/blob/master/HOCON.md"
+includes: { 
+  include required(file("~/prog/tree-sitter-hocon/grammar.js")) 
+//         ^keyword
+//^include
+//                ^punctuation.bracket
+//                                                           ^punctuation.bracket
+  override = true
+//            ^boolean
+}
+
+it's: ${it's}. A ${HOCON}
+//    ^punctuation.special
+//     ^punctuation.special
+//          ^punctuation.special
+//           ^string
+//             ^string
+//                ^punctuation.special
+//                      ^punctuation.special
+
+this.is.a."long.key" = null,
+//  ^punctuation.delimiter
+//     ^punctuation.delimiter
+//       ^punctuation.delimiter
+//                      ^constant.builtin
+week  = 7 days 
+//      ^number
+//         ^keyword
+
+