zig: Detect visual separators in integer literals

Zig docs: "// underscores may be placed between two digits as a visual
separator"

Author: nyaayaya

Diff for: lexers/z/zig.go

@@ -30,10 +30,10 @@ var Zig = internal.Register(MustNewLexer(
 			{`0x[0-9a-fA-F]+\.?[pP][\-+]?[0-9a-fA-F]+`, LiteralNumberFloat, nil},
 			{`[0-9]+\.[0-9]+([eE][-+]?[0-9]+)?`, LiteralNumberFloat, nil},
 			{`[0-9]+\.?[eE][-+]?[0-9]+`, LiteralNumberFloat, nil},
-			{`0b[01]+`, LiteralNumberBin, nil},
-			{`0o[0-7]+`, LiteralNumberOct, nil},
-			{`0x[0-9a-fA-F]+`, LiteralNumberHex, nil},
-			{`[0-9]+`, LiteralNumberInteger, nil},
+			{`0b(?:_?[01])+`, LiteralNumberBin, nil},
+			{`0o(?:_?[0-7])+`, LiteralNumberOct, nil},
+			{`0x(?:_?[0-9a-fA-F])+`, LiteralNumberHex, nil},
+			{`(?:_?[0-9])+`, LiteralNumberInteger, nil},
 			{`@[a-zA-Z_]\w*`, NameBuiltin, nil},
 			{`[a-zA-Z_]\w*`, Name, nil},
 			{`\'\\\'\'`, LiteralStringEscape, nil},