chore: set up routing with mock pages

src/pages/episode.tsx

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+export function Episode() {
+  return <h1>Episode page</h1>;
+}

src/pages/home.tsx

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+export function Home() {
+  return <h1>Home page</h1>;
+}

src/pages/podcast.tsx

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+export function Podcast() {
+  return <h1>Podcast page</h1>;
+}