rewrote yaml.nanorc to improve syntax highlighting

yaml.nanorc

@@ -1,13 +1,21 @@
-syntax "YAML" "\.ya?ml$"
+syntax yaml "\.ya?ml"
+comment "#"
 header "^---" "%YAML"
 
-color green     "(^| )!!(binary|bool|float|int|map|null|omap|seq|set|str) "
-color brightcyan  "\<(YES|yes|Y|y|ON|on|NO|no|N|n|OFF|off)\>"
-color brightcyan "\<(true|false)\>"
-color red ":[[:space:]]" "\[" "\]" ":[[:space:]]+[|>]" "^[[:space:]]*- "
-color brightyellow "[[:space:]][\*&][A-Za-z0-9]+"
-color yellow ""(\\.|[^"])*"|'(\\.|[^'])*'"
-color brightblack "(^|[[:space:]])#([^{].*)?$"
-color brightmagenta  "^---" "^\.\.\." "^%YAML" "^%TAG"
-color ,green "[[:space:]]+$"
-color ,red "	+ +| +	+"
+# Values
+color green "(:|^|\s)+\S+"
+
+# Keys
+color red "(^|\s+).*+\s*:(\s|$)"
+
+# Special values
+color yellow "[:-]\s+(true|false|null)\s*$"
+color yellow "[:-]\s+[0-9]+\.?[0-9]*(\s*($|#))"
+color yellow  "(^| )!!(binary|bool|float|int|map|null|omap|seq|set|str) "
+
+# Separator
+color brightwhite "^\s+-"
+color brightwhite ":(\s|\t|$)"
+
+# Comments
+color white "(^|[[:space:]])#.*$"