refactor: Add 'src' folder in 'site' (#445)

This refactoring re-organizes the `site` folder to have a nested `src` folder.

Originally, [we wanted to keep the directory structure shallow](https://github.com/coder/coder/pull/8#issuecomment-1009578910) - but there were two points that motivated this change to introduce the `src` level.

1. We have several non-`src` folders now (`e2e`, `static`, `html_templates`, `.storybook`)
2. Having a `src` folder makes it easier to run XState Typegen

So given those two data points - I believe it makes sense to revisit that and introduce a `src` folder.

site/src/components/CodeExample/CodeExample.tsx

@@ -0,0 +1,38 @@
+import { makeStyles } from "@material-ui/core/styles"
+import React from "react"
+import { MONOSPACE_FONT_FAMILY } from "../../theme/constants"
+
+import { CopyButton } from "../Button"
+
+export interface CodeExampleProps {
+  code: string
+}
+
+/**
+ * Component to show single-line code examples, with a copy button
+ */
+export const CodeExample: React.FC<CodeExampleProps> = ({ code }) => {
+  const styles = useStyles()
+
+  return (
+    <div className={styles.root}>
+      <code>{code}</code>
+      <CopyButton text={code} />
+    </div>
+  )
+}
+
+const useStyles = makeStyles((theme) => ({
+  root: {
+    display: "flex",
+    flexDirection: "row",
+    justifyContent: "space-between",
+    alignItems: "center",
+    background: theme.palette.background.default,
+    color: theme.palette.codeBlock.contrastText,
+    fontFamily: MONOSPACE_FONT_FAMILY,
+    fontSize: 13,
+    padding: theme.spacing(2),
+    borderRadius: theme.shape.borderRadius,
+  },
+}))