⚡ (whatsapp) Improve / fix markdown serializer

Forked remark-slate code to create Typebot's own serializer

Closes #1056

packages/lib/serializer/convertRichTextToMarkdown.ts

@@ -0,0 +1,41 @@
+import { TElement } from '@udecode/plate-common'
+import serialize from './serialize'
+import { defaultNodeTypes } from './ast-types'
+
+export const convertRichTextToMarkdown = (
+  richText: TElement[],
+  options?: { flavour?: 'common' | 'whatsapp' }
+) => {
+  let extraNewLinesCount = 0
+  const test = richText
+    .reduce<string[]>((acc, node) => {
+      if (node.type === 'variable' || node.type === 'inline-variable') {
+        return [
+          ...acc,
+          ...node.children.map(
+            (child) =>
+              serialize(child, {
+                nodeTypes: defaultNodeTypes,
+                flavour: options?.flavour,
+              }) as string
+          ),
+        ]
+      }
+      const serializedElement = serialize(node, {
+        nodeTypes: defaultNodeTypes,
+        flavour: options?.flavour,
+      })
+      if (!serializedElement || serializedElement === '<br>\n\n') {
+        if (extraNewLinesCount > 0) {
+          return [...acc, '']
+        }
+        extraNewLinesCount++
+        return acc
+      }
+      extraNewLinesCount = 0
+      return [...acc, serializedElement]
+    }, [])
+    .join('\n')
+
+  return test.endsWith('\n') ? test.slice(0, -2) : test
+}