Add comment about level 1 Unicode properties

Author: slevithan

tools/scripts/property-regex.js

@@ -4,6 +4,10 @@ const {
     unicodeVersion
 } = require('./utils.js');
 
+// This intentially includes only the binary properties required by UTS 18 Level 1 RL1.2 for Unicode
+// regex support, minus `Assigned` which has special handling since it is the inverse of Unicode
+// category `Unassigned` (`Cn`). To include all binary properties, change this to:
+// `const properties = require(`${unicodeVersion}`).Binary_Property;`
 const properties = [
     'ASCII',
     'Alphabetic',