syntax: javascript: color strings differently from major keywords

Also, remove the coloring of special single-quoted strings as they
get recolored by the subsequent general string-coloring command.

And remove the coloring of all-uppercase words, as other editors
do not color those either.

syntax/javascript.nanorc

@@ -3,15 +3,13 @@
 syntax "javascript" "\.js$"
 comment "//"
 
-color brightred "\<[A-Z_][0-9A-Z_]+\>"
 color green "\<(async|class|const|extends|function|let|this|typeof|var|void)\>"
 color brightyellow "\<(for|if|while|with|do|else|case|default|switch)\>"
 color brightyellow "\<(await|export|import|try|throw|catch|new|delete)\>"
 color magenta "\<(continue|break|return|yield)\>"
-color brightmagenta "'([^'\]|(\\["'abfnrtv\\]))'" "'\\(([0-3]?[0-7]{1,2}))'" "'\\x[0-9A-Fa-f]{1,2}'"
 
 # Strings.
-color brightyellow "<[^= 	]*>" ""(\\.|[^"])*"" "'(\\.|[^'])*'" "`(\\.|[^`])*`"
+color brightmagenta "<[^= 	]*>" ""(\\.|[^"])*"" "'(\\.|[^'])*'" "`(\\.|[^`])*`"
 # Comments.
 color brightblue "(^|[[:space:]])//.*"
 color brightblue start="/\*" end="\*/"