feat: initialize markr nostr bookmark client

- Add project structure with TypeScript, React, and Vite
- Implement nostr authentication using browser extension (NIP-07)
- Add NIP-51 compliant bookmark fetching and display
- Create minimal UI with login and bookmark components
- Integrate applesauce-core and applesauce-react libraries
- Add responsive styling with dark/light mode support
- Include comprehensive README with setup instructions

This is a minimal MVP for a nostr bookmark client that allows users to
view their bookmarks according to NIP-51 specification.

node_modules/mdast-util-to-markdown/lib/join.js

@@ -0,0 +1,39 @@
+/**
+ * @import {Join} from 'mdast-util-to-markdown'
+ */
+
+import {formatCodeAsIndented} from './util/format-code-as-indented.js'
+import {formatHeadingAsSetext} from './util/format-heading-as-setext.js'
+
+/** @type {Array<Join>} */
+export const join = [joinDefaults]
+
+/** @type {Join} */
+function joinDefaults(left, right, parent, state) {
+  // Indented code after list or another indented code.
+  if (
+    right.type === 'code' &&
+    formatCodeAsIndented(right, state) &&
+    (left.type === 'list' ||
+      (left.type === right.type && formatCodeAsIndented(left, state)))
+  ) {
+    return false
+  }
+
+  // Join children of a list or an item.
+  // In which case, `parent` has a `spread` field.
+  if ('spread' in parent && typeof parent.spread === 'boolean') {
+    if (
+      left.type === 'paragraph' &&
+      // Two paragraphs.
+      (left.type === right.type ||
+        right.type === 'definition' ||
+        // Paragraph followed by a setext heading.
+        (right.type === 'heading' && formatHeadingAsSetext(right, state)))
+    ) {
+      return
+    }
+
+    return parent.spread ? 1 : 0
+  }
+}