fix(markdown): keep custom inline elements inside table cell paragraphs (udecode#5068)

Author: WilliamPeralta

.changeset/tidy-pugs-punch.md

@@ -0,0 +1,5 @@
+---
+'@platejs/markdown': patch
+---
+
+Keep custom inline elements inside a table cell's paragraph when deserializing markdown. The cell deserializer recognised only `inlineEquation` as inline, so any other custom inline element was hoisted out of the paragraph and became its sibling. The cell serializer then separated those siblings with `<br/>`, and a second round trip turned that into a newline — silently destroying the element. The check now asks the editor whether the node is inline, which is the same answer the plugin configuration already holds.

packages/markdown/src/lib/rules/defaultRules.ts

@@ -964,7 +964,11 @@ export const defaultRules: MdRules = {
 
               for (const child of cellChildren) {
                 // Text nodes or inline elements should be grouped into paragraphs
-                if (!child.type || child.type === KEYS.inlineEquation) {
+                if (
+                  !child.type ||
+                  child.type === KEYS.inlineEquation ||
+                  options.editor!.api.isInline(child)
+                ) {
                   currentParagraphChildren.push(child);
                 } else {
                   // Block-level elements should end the current paragraph and be added directly