Gatsby.jsでMDXを使っている場合にRSSフィードを追加する方法【gatsby-plugin-feed】

Error: Cannot query field "html" on type "Mdx". GraphQL request

module.exports = {
  plugins: [
    {
      resolve: `gatsby-plugin-feed`,
      options: {
        query: `
          {
            site {
              siteMetadata {
                title
                description
                siteUrl
                site_url: siteUrl
              }
            }
          }
        `,
        feeds: [
          {
-           serialize: ({ query: { site, allMarkdownRemark } }) => {
-             return allMarkdownRemark.nodes.map(node => {
+           serialize: ({ query: { site, allMdx } }) => {
+             return allMdx.nodes.map(node => {
                return Object.assign({}, node.frontmatter, {
                  description: node.excerpt,
                  date: node.frontmatter.date,
                  url: site.siteMetadata.siteUrl + node.fields.slug,
                  guid: site.siteMetadata.siteUrl + node.fields.slug,
-                 custom_elements: [{ "content:encoded": node.html }],
                })
              })
            },
            query: `
              {
-               allMarkdownRemark(
+               allMdx(
                  sort: { order: DESC, fields: [frontmatter___date] },
                ) {
                  nodes {
                    excerpt
-                   html
                    fields { 
                      slug 
                    }
                    frontmatter {
                      title
                      date
                    }
                  }
                }
              }
            `,
            output: "/rss.xml",
            title: "Your Site's RSS Feed",
            // optional configuration to insert feed reference in pages:
            // if `string` is used, it will be used to create RegExp and then test if pathname of
            // current page satisfied this regular expression;
            // if not provided or `undefined`, all pages will have feed reference inserted
            match: "^/blog/",
            // optional configuration to specify external rss feed, such as feedburner
            link: "https://feeds.feedburner.com/gatsby/blog",
          },
        ],
      },
    },
  ],
}