config: enable toml syntax highlighting

docusaurus doesn't enable toml highlighting by default, let's enable it

See the following links for the list of languages enabled by default:
https://docusaurus.io/docs/markdown-features/code-blocks#supported-languages
https://github.com/FormidableLabs/prism-react-renderer/blob/master/packages/generate-prism-languages/index.ts#L9-L23

docusaurus.config.ts

@@ -138,6 +138,7 @@ const config: Config = {
     prism: {
       theme: prismThemes.github,
       darkTheme: prismThemes.dracula,
+      additionalLanguages: ['toml'],
     },
   } satisfies Preset.ThemeConfig,
   plugins: [