Style of vue-markdown not show with vue template

[Navyroot]

My code :

<template>
  <div>
    <VueMarkdown :source="fileContent"></VueMarkdown>
  </div>
</template>
<script>
import VueMarkdown from 'vue-markdown'

import fileMd from 'raw-loader!../README.md'
export default {
  name: 'app',
  // extends: mdFile.vue.component,
  components: { VueMarkdown },
  data() {
    return {
      fileContent: '## __Hello__',
    }
  },
  mounted() {
    this.fileContent = fileMd
    // eslint-disable-next-line no-console
    console.log('fileMd', fileMd)
  },
}
</script>

Markdown script :

Result on my page :

Result on demo page :