docs: Clarifications in the Explorer Docs (#938)

add example to filter by tags.

docs/features/explorer.md

@@ -61,7 +61,7 @@ export class FileNode {
   children: FileNode[]  // children of current node
   name: string  // last part of slug
   displayName: string // what actually should be displayed in the explorer
-  file: QuartzPluginData | null // set if node is a file, see `QuartzPluginData` for more detail
+  file: QuartzPluginData | null // if node is a file, this is the file's metadata. See `QuartzPluginData` for more detail
   depth: number // depth of current node
 
   ... // rest of implementation
@@ -167,6 +167,19 @@ Component.Explorer({
 
 You can customize this by changing the entries of the `omit` set. Simply add all folder or file names you want to remove.
 
+### Remove files by tag
+
+You can access the frontmatter of a file by `node.file?.frontmatter?`. This allows you to filter out files based on their frontmatter, for example by their tags.
+
+```ts title="quartz.layout.ts"
+Component.Explorer({
+  filterFn: (node) => {
+    // exclude files with the tag "explorerexclude"
+    return node.file?.frontmatter?.tags?.includes("explorerexclude") !== true
+  },
+})
+```
+
 ### Show every element in explorer
 
 To override the default filter function that removes the `tags` folder from the explorer, you can set the filter function to `undefined`.