syntax: javascript: add some comments, and color explicit numbers too

syntax/javascript.nanorc

-## Here is an example for Javascript.
+## Syntax highlighting for Javascript.
 
 syntax "javascript" "\.js$"
 comment "//"
 
+# Declarational stuff.
 color green "\<(async|class|const|extends|function|let|this|typeof|var|void)\>"
+# Flow control and special keywords.
 color brightyellow "\<(do|while|if|else|switch|case|default|for|each|in|of|with)\>"
 color brightyellow "\<(await|export|import|throw|try|catch|finally|new|delete)\>"
+# "Exit" points.
 color magenta "\<(break|continue|return|yield)\>"
 
+# Octal/decimal and hexadecimal numbers.
+color cyan "\<[0-9]+\>" "\<0x[0-9A-Fa-f]+\>"
+
 # Strings.
 color brightmagenta ""(\\.|[^"])*"" "'(\\.|[^'])*'" "`(\\.|[^`])*`"
 # Comments.