kotlin: add sealed as a class modifier

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

kotlin.nanorc

@@ -8,7 +8,7 @@
 syntax "kotlin" "\.kt$" "\.kts$"
 color magenta "\b(([1-9][0-9]+)|0+)\.[0-9]+\b" "\b[1-9][0-9]*\b" "\b0[0-7]*\b" "\b0x[1-9a-f][0-9a-f]*\b"
 color yellow "[.:;,+*|=!\%@]" "<" ">" "/" "-" "&"
-color green "\<(namespace|as|type|class|this|super|val|var|fun|is|in|object|when|trait|import|where|by|get|set|abstract|enum|open|annotation|override|private|public|internal|protected|out|vararg|inline|final|package|lateinit|constructor|companion|const|suspend)\>"
+color green "\<(namespace|as|type|class|this|super|val|var|fun|is|in|object|when|trait|import|where|by|get|set|abstract|enum|open|annotation|override|private|public|internal|protected|out|vararg|inline|final|package|lateinit|constructor|companion|const|suspend|sealed)\>"
 color yellow "\<(true|false|null)\>"
 color cyan "\<(break|catch|continue|do|else|finally|for|if|return|throw|try|while|repeat)\>"
 color brightred "\<(inner|outer)\>"