Highlight more language elements

extensions/vscode/spec/grammar.tmLanguage.json

@@ -1,4 +1,5 @@
 {
+  "$schema": "https://raw.githubusercontent.com/martinring/tmlanguage/master/tmlanguage.json",
   "scopeName": "source.kyanite",
   "patterns": [{ "include": "#expression" }],
   "repository": {
@@ -9,9 +10,11 @@
         { "include": "#record-impl-decl" },
         { "include": "#strings" },
         { "include": "#numbers" },
+        { "include": "#booleans" },
         { "include": "#functions" },
         { "include": "#keyword" },
         { "include": "#operators" },
+        { "include": "#builtin-types" },
         { "include": "#paren-expression" },
         { "include": "#comment" }
       ]
@@ -45,6 +48,10 @@
       "name": "constant.numeric.kyanite",
       "match": "\\b[0-9]+\\b(.[0-9]+)?\\b"
     },
+    "booleans": {
+      "name": "constant.language.boolean.kyanite",
+      "match": "\\b(true|false)\\b"
+    },
     "operators": {
       "name": "keyword.operator.kyanite",
       "match": "[\\+\\-\\/\\*]"
@@ -56,12 +63,16 @@
         "1": { "name": "keyword.kyanite" }
       }
     },
+    "builtin-types": {
+      "match": "\\b(int|str|bool)\\b",
+      "name": "entity.name.type.kyanite"
+    },
     "keyword": {
       "match": "\\b(let|const|fun|impl)\\b",
       "name": "keyword.kyanite"
     },
     "control-flow": {
-      "match": "\\b(if|else|while|for|in)\\b",
+      "match": "\\b(if|else|while|for|in|return)\\b",
       "name": "keyword.control.kyanite"
     },
     "record-impl-decl": {