docs: add some simple benchmark for markdown (#3)

README.md

@@ -28,6 +28,18 @@ if err != nil {
 fmt.Println(output)
 // Output: H1 \nitalic bold code `not code link image strikethrough
 ```
+#### Benchmark
+```shell
+goos: windows
+goarch: amd64
+pkg: github.com/huantt/plaintext-extractor/markdown
+cpu: 11th Gen Intel(R) Core(TM) i5-1155G7 @ 2.50GHz
+BenchmarkMarkdownExtractorMediumSize
+BenchmarkMarkdownExtractorMediumSize-8   	12194006	        89.09 ns/op	      16 B/op	       1 allocs/op
+BenchmarkMarkdownExtractorLargeSize
+BenchmarkMarkdownExtractorLargeSize-8    	12645927	        88.25 ns/op	      16 B/op	       1 allocs/op
+PASS
+```
 
 ### Custom Markdown Tag
 ```go

markdown/extractor_test.go

@@ -2,9 +2,11 @@ package markdown
 
 import (
 	"fmt"
-	"github.com/stretchr/testify/assert"
+	"os"
 	"regexp"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestExtract(t *testing.T) {
@@ -54,3 +56,25 @@ func TestCustomTag(t *testing.T) {
 		assert.Equal(t, test.expected, *output)
 	}
 }
+
+func BenchmarkMarkdownExtractorMediumSize(b *testing.B) {
+	data, _ := os.ReadFile("testdata/markdown/go-validator.md")
+	input := string(data)
+
+	extractor := NewExtractor()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, _ = extractor.PlainText(input)
+	}
+}
+
+func BenchmarkMarkdownExtractorLargeSize(b *testing.B) {
+	data, _ := os.ReadFile("testdata/markdown/awesome-go.md")
+	input := string(data)
+
+	extractor := NewExtractor()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, _ = extractor.PlainText(input)
+	}
+}