DodoApp: Use picocss for UI

Change-Id: I2d610c4f57e4dfbbe566a7c7f82147443e0106f1
diff --git a/core/installer/welcome/dodo-app-tmpl/base.html b/core/installer/welcome/dodo-app-tmpl/base.html
new file mode 100644
index 0000000..85b480e
--- /dev/null
+++ b/core/installer/welcome/dodo-app-tmpl/base.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html lang="en" data-theme="light">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>{{ block "title" . }}{{ end }}</title>
+    <link rel="stylesheet" href="/static/pico.2.0.6.min.css">
+    <link rel="stylesheet" href="/static/dodo_app.css?v=0.0.3">
+</head>
+<body class="container">
+    {{- block "content" . }}
+    {{- end }}
+</body>
+</html>