feat: add reactions (#1074)

reaction/action/webhook/payload.go

@@ -0,0 +1,20 @@
+package webhook
+
+import (
+	"encoding/base64"
+	"io"
+	"unicode/utf8"
+)
+
+func EncodeBody(requestBody io.Reader) (string, bool) {
+	body, err := io.ReadAll(requestBody)
+	if err != nil {
+		return "", false
+	}
+
+	if utf8.Valid(body) {
+		return string(body), false
+	}
+
+	return base64.StdEncoding.EncodeToString(body), true
+}