add support for creating rooms

Fixes #81

lib/widgets/sheet_layout.dart

@@ -0,0 +1,29 @@
+import "package:material_ui/material_ui.dart";
+
+class const SheetLayout({
+  required final Widget title,
+  required final List<Widget> children,
+  required final List<Widget> actions,
+  super.key,
+}) extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) => Padding(
+    padding: .only(bottom: MediaQuery.viewInsetsOf(context).bottom),
+    child: SingleChildScrollView(
+      padding: const .all(24),
+      child: Column(
+        mainAxisSize: .min,
+        crossAxisAlignment: .stretch,
+        spacing: 12,
+        children: [
+          DefaultTextStyle(
+            style: Theme.of(context).textTheme.headlineSmall!,
+            child: title,
+          ),
+          ...children,
+          Row(mainAxisAlignment: .end, spacing: 8, children: actions),
+        ],
+      ),
+    ),
+  );
+}