build(deps): bump gatsby-plugin-manifest in /gatsby-theme-mate

Bumps [gatsby-plugin-manifest](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-manifest) from 4.25.0 to 5.12.3.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-manifest/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-plugin-manifest@5.12.3/packages/gatsby-plugin-manifest)

---
updated-dependencies:
- dependency-name: gatsby-plugin-manifest
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

gatsby-theme-mate/package.json

@@ -38,7 +38,7 @@
     "babel-plugin-styled-components": "^2.1.4",
     "gatsby-plugin-fontawesome-css": "^1.2.0",
     "gatsby-plugin-image": "^2.10.0",
-    "gatsby-plugin-manifest": "^4.10.1",
+    "gatsby-plugin-manifest": "^5.12.3",
     "gatsby-plugin-react-helmet": "^5.10.0",
     "gatsby-plugin-sharp": "^4.25.1",
     "gatsby-plugin-styled-components": "^5.10.0",