replace mui buttons, move them into bar

client/src/components/Button.tsx

@@ -0,0 +1,14 @@
+import * as React from 'react';
+import { Link, LinkProps } from "react-router-dom";
+
+export interface ButtonProps extends LinkProps {
+  disabled?: boolean
+}
+
+export function Button(props: ButtonProps) {
+  if (props.disabled) {
+    return <span className="btn btn-disabled" {...props}>{props.children}</span>
+  } else {
+    return <Link className="btn" {...props}>{props.children}</Link>
+  }
+}