Add ansi.StyleWriter, which wrap writer's output into a style

ansi/stylewriter.go

@@ -0,0 +1,28 @@
+package ansi
+
+import (
+	"bytes"
+	"io"
+)
+
+type StyleWriter struct {
+	w     io.Writer
+	buf   bytes.Buffer
+	rules StylePrimitive
+}
+
+func NewStyleWriter(ctx RenderContext, w io.Writer, rules StylePrimitive) *StyleWriter {
+	return &StyleWriter{
+		w:     w,
+		rules: rules,
+	}
+}
+
+func (w *StyleWriter) Write(b []byte) (int, error) {
+	return w.buf.Write(b)
+}
+
+func (w *StyleWriter) Close() error {
+	renderText(w.w, w.rules, w.buf.String())
+	return nil
+}