[rest] Redoc page uses UTF-8 charset

Author: liyubin117

docs/layouts/partials/docs/inject/head.html

@@ -24,5 +24,7 @@
 <script src="{{.Site.BaseURL}}/js/flink.js"></script>
 <!-- Only takes effect when the `redocPage` variable is true. -->
 {{ if .Params.redocPage }}
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <script src="{{.Site.BaseURL}}/js/redoc.standalone.js"></script>
 {{ end }}