syntax: nanorc: don't color the argument of 'linter' as if invalid

Color it bright green instead, like valid numeric arguments of
'fill' and 'tabsize'.  Also color the argument of 'formatter'.

syntax/nanorc.nanorc

@@ -4,7 +4,7 @@ syntax "nanorc" "\.?nanorc$"
 comment "#"
 
 # Possible errors and parameters
-icolor brightred "^[[:space:]]*((un)?(bind|set)|include|syntax|header|comment|magic|linter|i?color|extendsyntax).*$"
+icolor brightred "^[[:space:]]*((un)?(bind|set)|include|syntax|header|magic|comment|linter|formatter|i?color|extendsyntax).*$"
 
 # Keywords
 icolor brightgreen "^[[:space:]]*(set|unset)[[:space:]]+(allow_insecure_backup|atblanks|autoindent|backup|backwards|boldtext|casesensitive|constantshow|cut|fill[[:space:]]+-?[[:digit:]]+|historylog|justifytrim|linenumbers|locking|morespace|mouse|multibuffer|noconvert|nohelp|nopauses|nonewlines|nowrap|positionlog|preserve|quickblank|quiet|rebinddelete|rebindkeypad|regexp|showcursor|smarthome|smooth|softwrap|suspend|tabsize[[:space:]]+[1-9][0-9]*|tabstospaces|tempfile|unix|view|wordbounds)\>"
@@ -13,6 +13,7 @@ icolor brightgreen "^[[:space:]]*set[[:space:]]+(backupdir|brackets|functioncolo
 icolor brightgreen "^[[:space:]]*bind[[:space:]]+((\^([[:alpha:]]|[]0-9\^_]|Space)|M-([[:alpha:]]|[]!"#$%&'()*+,./0-9:;<=>?@\^_`{|}~-]|Space))|F([1-9]|1[0-6])|Ins|Del)[[:space:]]+[[:alpha:]]+[[:space:]]+(all|main|search|replace(with)?|gotoline|writeout|insert|ext(ernal)?cmd|help|spell|linter|browser|whereisfile|gotodir)([[:space:]]+#|[[:space:]]*$)"
 icolor brightgreen "^[[:space:]]*unbind[[:space:]]+((\^([[:alpha:]]|[]0-9\^_]|Space)|M-([[:alpha:]]|[]!"#$%&'()*+,./0-9:;<=>?@\^_`{|}~-]|Space))|F([1-9]|1[0-6])|Ins|Del)[[:space:]]+(all|main|search|replace(with)?|gotoline|writeout|insert|ext(ernal)?cmd|help|spell|linter|browser|whereisfile|gotodir)([[:space:]]+#|[[:space:]]*$)"
 icolor brightgreen "^[[:space:]]*extendsyntax[[:space:]]+[[:alpha:]]+[[:space:]]+(i?color|header|magic|comment|linter|formatter)[[:space:]]+.*$"
+icolor brightgreen "^[[:space:]]*(linter|formatter)[[:space:]]+[[:alpha:]]+"
 icolor green "^[[:space:]]*((un)?(bind|set)|include|syntax|header|magic|comment|linter|formatter|extendsyntax)\>"
 
 # Colors