Add client context.

src/context/revoltjs/CheckAuth.tsx

@@ -0,0 +1,22 @@
+import { ReactNode } from "react";
+import { useContext } from "preact/hooks";
+import { Redirect } from "react-router-dom";
+
+import { AppContext } from "./RevoltClient";
+
+interface Props {
+    auth?: boolean;
+    children: ReactNode | ReactNode[];
+}
+
+export const CheckAuth = (props: Props) => {
+    const { operations } = useContext(AppContext);
+
+    if (props.auth && !operations.ready()) {
+        return <Redirect to="/login" />;
+    } else if (!props.auth && operations.ready()) {
+        return <Redirect to="/" />;
+    }
+
+    return <>{props.children}</>;
+};