chore(deps): bump chroma to v2 #735

Bump `alecthomas/chroma` to `v2`:
https://github.com/cheat/cheat/issues/735

vendor/github.com/alecthomas/chroma/v2/lexers/markdown.go

@@ -0,0 +1,47 @@
+package lexers
+
+import (
+	. "github.com/alecthomas/chroma/v2" // nolint
+)
+
+// Markdown lexer.
+var Markdown = Register(DelegatingLexer(HTML, MustNewLexer(
+	&Config{
+		Name:      "markdown",
+		Aliases:   []string{"md", "mkd"},
+		Filenames: []string{"*.md", "*.mkd", "*.markdown"},
+		MimeTypes: []string{"text/x-markdown"},
+	},
+	markdownRules,
+)))
+
+func markdownRules() Rules {
+	return Rules{
+		"root": {
+			{`^(#[^#].+\n)`, ByGroups(GenericHeading), nil},
+			{`^(#{2,6}.+\n)`, ByGroups(GenericSubheading), nil},
+			{`^(\s*)([*-] )(\[[ xX]\])( .+\n)`, ByGroups(Text, Keyword, Keyword, UsingSelf("inline")), nil},
+			{`^(\s*)([*-])(\s)(.+\n)`, ByGroups(Text, Keyword, Text, UsingSelf("inline")), nil},
+			{`^(\s*)([0-9]+\.)( .+\n)`, ByGroups(Text, Keyword, UsingSelf("inline")), nil},
+			{`^(\s*>\s)(.+\n)`, ByGroups(Keyword, GenericEmph), nil},
+			{"^(```\\n)([\\w\\W]*?)(^```$)", ByGroups(String, Text, String), nil},
+			{
+				"^(```)(\\w+)(\\n)([\\w\\W]*?)(^```$)",
+				UsingByGroup(2, 4, String, String, String, Text, String),
+				nil,
+			},
+			Include("inline"),
+		},
+		"inline": {
+			{`\\.`, Text, nil},
+			{`(\s)(\*|_)((?:(?!\2).)*)(\2)((?=\W|\n))`, ByGroups(Text, GenericEmph, GenericEmph, GenericEmph, Text), nil},
+			{`(\s)((\*\*|__).*?)\3((?=\W|\n))`, ByGroups(Text, GenericStrong, GenericStrong, Text), nil},
+			{`(\s)(~~[^~]+~~)((?=\W|\n))`, ByGroups(Text, GenericDeleted, Text), nil},
+			{"`[^`]+`", LiteralStringBacktick, nil},
+			{`[@#][\w/:]+`, NameEntity, nil},
+			{`(!?\[)([^]]+)(\])(\()([^)]+)(\))`, ByGroups(Text, NameTag, Text, Text, NameAttribute, Text), nil},
+			{`[^\\\s]+`, Other, nil},
+			{`.|\n`, Other, nil},
+		},
+	}
+}