Add some missing keywords.

Author: tamdaz

languages/crystal/highlights.scm

@@ -1,6 +1,7 @@
 [
   "alias"
   "annotation"
+  "asm"
   "begin"
   "break"
   "case"
@@ -18,24 +19,33 @@
   "if"
   "in"
   "include"
+  "instance_sizeof"
   "lib"
   "macro"
   "module"
   "next"
   "of"
+  "out"
+  "pointerof"
+  "previous_def"
   "require"
   "rescue"
   "return"
   "select"
+  "sizeof"
   "struct"
+  "super"
   "then"
   "type"
+  "typeof"
+  "uninitialized"
   "union"
   "unless"
   "until"
   "verbatim"
   "when"
   "while"
+  "with"
   "yield"
 ] @keyword