chore: Move to Typescript (#2783)

This PR moves the entire project to Typescript. Due to the ~1000 ignores this will lead to a messy codebase for a while, but the churn is worth it – all of those ignore comments are places that were never type-safe previously.

closes #1282

app/components/ContextMenu/Separator.tsx

@@ -0,0 +1,15 @@
+import * as React from "react";
+import { MenuSeparator } from "reakit/Menu";
+import styled from "styled-components";
+
+export default function Separator(rest: any) {
+  return (
+    <MenuSeparator {...rest}>
+      {(props) => <HorizontalRule {...props} />}
+    </MenuSeparator>
+  );
+}
+
+const HorizontalRule = styled.hr`
+  margin: 0.5em 12px;
+`;