Add csv file render support defaultly (#4105)

* add csv file render support defaultly

* escaping csv column content

modules/markup/csv/csv_test.go

@@ -0,0 +1,25 @@
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package markup
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRenderCSV(t *testing.T) {
+	var parser Parser
+	var kases = map[string]string{
+		"a":     "<table class=\"table\"><tr><td>a</td><tr></table>",
+		"1,2":   "<table class=\"table\"><tr><td>1</td><td>2</td><tr></table>",
+		"<br/>": "<table class=\"table\"><tr><td>&lt;br/&gt;</td><tr></table>",
+	}
+
+	for k, v := range kases {
+		res := parser.Render([]byte(k), "", nil, false)
+		assert.EqualValues(t, v, string(res))
+	}
+}