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/worker-constants.ts

@@ -0,0 +1,23 @@
+import { StepExecutionResult } from "./types";
+
+export type WorkerRequestData =
+  | {
+      type: "Init";
+      params?: null;
+    }
+  | {
+      type: "Reset";
+      params?: null;
+    }
+  | {
+      type: "Prepare";
+      params: { code: string; input: string };
+    }
+  | {
+      type: "Execute";
+      params: { interval?: number };
+    };
+
+export type WorkerResponseData<RS> =
+  | { type: "state"; data: "empty" | "ready" }
+  | { type: "result"; data: StepExecutionResult<RS> };