Implement basic execution system and UI

This is a rather large commit that includes all of the following:
- React UI with code editor, runtime renderer and input-output panes
- Language providers for a sample language and Brainfuck
- Implementation of code execution in a web worker
- All-at-once unabortable execution of program fully functional

engines/sample-lang/renderer.tsx

@@ -0,0 +1,24 @@
+import { RendererProps } from "../types";
+import { RS } from "./constants";
+
+const styles = {
+  container: {
+    width: "100%",
+    height: "100%",
+    display: "flex",
+    alignItems: "center",
+    justifyContent: "center",
+  },
+  text: {
+    fontSize: "4em",
+  },
+};
+
+export const Renderer = ({ state }: RendererProps<RS>) => {
+  const value = state == null ? 0 : state.value;
+  return (
+    <div style={styles.container}>
+      <h1 style={styles.text}>{value}</h1>
+    </div>
+  );
+};