Add GUIDE section for v3 docs

docs/en/guide/extensions.md

@@ -1,3 +1,17 @@
+<script setup>
+import SearchTable from "../../.vitepress/components/SearchTable.vue";
+</script>
+
 # Supported Extensions
 
-<!-- TODO: Auto-generated by `bin/spc dev:gen-ext-docs`. Placeholder until command is implemented in v3. -->
+> - ✅: Supported
+> - blank: Not supported or not yet ported
+
+<search-table />
+
+::: tip
+If an extension you need is missing, you can file a [feature request](https://github.com/crazywhalecc/static-php-cli/issues).
+
+Some extensions or their library dependencies have optional features (e.g. gd can optionally use libwebp, freetype, etc.).
+Running `bin/spc build gd --build-cli` alone will not include them — StaticPHP follows a minimal-dependency principle by default.
+:::