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

styles/editor.css

@@ -0,0 +1,12 @@
+.code-highlight {
+  background-color: #ffff0077;
+}
+
+.breakpoint-glyph {
+  box-sizing: border-box;
+  padding: 4%;
+  border-radius: 50%;
+  margin-left: 10px;
+  background-color: #ff5555;
+  background-clip: content-box;
+}

styles/globals.css

@@ -0,0 +1,23 @@
+@import "@blueprintjs/core/lib/css/blueprint.css";
+@import "@blueprintjs/icons/lib/css/blueprint-icons.css";
+@import "react-mosaic-component/react-mosaic-component.css";
+
+html,
+body,
+#__next {
+  padding: 0;
+  margin: 0;
+  width: 100%;
+  height: 100vh;
+  font-family: -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Oxygen,
+    Ubuntu, Cantarell, Fira Sans, Droid Sans, Helvetica Neue, sans-serif;
+}
+
+a {
+  color: inherit;
+  text-decoration: none;
+}
+
+* {
+  box-sizing: border-box;
+}