feat: add table cell background color picker

- Extended TableCell and TableHeader to support backgroundColor attribute
- Created TableBackgroundColor component with 21 color options
- Integrated color picker into table cell menu using Mantine UI
- Added support for both regular cells and header cells
- Updated imports to use custom TableHeader from @docmost/editor-ext

packages/editor-ext/src/lib/table/cell.ts

@@ -3,4 +3,22 @@ import { TableCell as TiptapTableCell } from "@tiptap/extension-table-cell";
 export const TableCell = TiptapTableCell.extend({
   name: "tableCell",
   content: "paragraph+",
+  
+  addAttributes() {
+    return {
+      ...this.parent?.(),
+      backgroundColor: {
+        default: null,
+        parseHTML: (element) => element.style.backgroundColor || null,
+        renderHTML: (attributes) => {
+          if (!attributes.backgroundColor) {
+            return {};
+          }
+          return {
+            style: `background-color: ${attributes.backgroundColor}`,
+          };
+        },
+      },
+    };
+  },
 });

packages/editor-ext/src/lib/table/header.ts

@@ -0,0 +1,24 @@
+import { TableHeader as TiptapTableHeader } from "@tiptap/extension-table-header";
+
+export const TableHeader = TiptapTableHeader.extend({
+  name: "tableHeader",
+  content: "paragraph+",
+  
+  addAttributes() {
+    return {
+      ...this.parent?.(),
+      backgroundColor: {
+        default: null,
+        parseHTML: (element) => element.style.backgroundColor || null,
+        renderHTML: (attributes) => {
+          if (!attributes.backgroundColor) {
+            return {};
+          }
+          return {
+            style: `background-color: ${attributes.backgroundColor}`,
+          };
+        },
+      },
+    };
+  },
+});

packages/editor-ext/src/lib/table/index.ts

@@ -1,2 +1,3 @@
 export * from "./row";
 export * from "./cell";
+export * from "./header";