material: rename mui to theme

src/material/theme.ts

@@ -0,0 +1,17 @@
+import { Theme, createTheme } from "@suid/material/styles";
+import { deepPurple, amber } from "@suid/material/colors";
+import { Accessor } from "solid-js";
+
+export function useRootTheme(): Accessor<Theme> {
+  return () =>
+    createTheme({
+      palette: {
+        primary: {
+          main: deepPurple[500],
+        },
+        secondary: {
+          main: amber.A200,
+        },
+      },
+    });
+}