docs: restore the Mesh, curves & text category lost in the README example index (#85)

Commit dcb9b0a dropped the </details>/<details> boundary between the
Materials and Mesh categories, folding fourteen examples under a header
that claims six. Restores the "Mesh, curves & text" summary (now 8
examples, vse-cut-list having since joined that table). All six category
headers again match their contents; the 26 total is unchanged.

Signed-off-by: fOuttaMyPaint <TMhospitalitystrategies@gmail.com>

Author: TMHSDigital

README.md

@@ -183,6 +183,11 @@ byte images stay straight 8-bit. Also witnesses `EXR color_mode='RGB'` dropping
 </tr>
 </table>
 
+</details>
+
+<details>
+<summary><strong>Mesh, curves &amp; text</strong> — 8 examples</summary>
+
 <table>
 <tr>
 <td width="46%" valign="middle">