Update chroma (#18033)

Update chroma to 0.9.4

Signed-off-by: Andrew Thornton <art27@cantab.net>

vendor/github.com/alecthomas/chroma/lexers/s/sieve.go

@@ -0,0 +1,37 @@
+package s
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Sieve lexer.
+var Sieve = internal.Register(MustNewLazyLexer(
+	&Config{
+		Name:      "Sieve",
+		Aliases:   []string{"sieve"},
+		Filenames: []string{"*.siv", "*.sieve"},
+		MimeTypes: []string{},
+	},
+	func() Rules {
+		return Rules{
+			"root": {
+				{`\s+`, Text, nil},
+				{`[();,{}\[\]]`, Punctuation, nil},
+				{`(?i)require`, KeywordNamespace, nil},
+				{`(?i)(:)(addresses|all|contains|content|create|copy|comparator|count|days|detail|domain|fcc|flags|from|handle|importance|is|localpart|length|lowerfirst|lower|matches|message|mime|options|over|percent|quotewildcard|raw|regex|specialuse|subject|text|under|upperfirst|upper|value)`, ByGroups(NameTag, NameTag), nil},
+				{`(?i)(address|addflag|allof|anyof|body|discard|elsif|else|envelope|ereject|exists|false|fileinto|if|hasflag|header|keep|notify_method_capability|notify|not|redirect|reject|removeflag|setflag|size|spamtest|stop|string|true|vacation|virustest)`, NameBuiltin, nil},
+				{`(?i)set`, KeywordDeclaration, nil},
+				{`([0-9.]+)([kmgKMG])?`, ByGroups(LiteralNumber, LiteralNumber), nil},
+				{`#.*$`, CommentSingle, nil},
+				{`/\*.*\*/`, CommentMultiline, nil},
+				{`"[^"]*?"`, LiteralString, nil},
+				{`text:`, NameTag, Push("text")},
+			},
+			"text": {
+				{`[^.].*?\n`, LiteralString, nil},
+				{`^\.`, Punctuation, Pop(1)},
+			},
+		}
+	},
+))