Refactor bot. (#8)

src/version.ts

@@ -0,0 +1,11 @@
+let cachedVer: string;
+let cachedTimestamp: number;
+
+export async function getLatest(): Promise<string> {
+  if (cachedVer && Date.now() - cachedTimestamp < 600000) return cachedVer; // 10min
+  const f = await fetch('https://api.github.com/repos/PolyMC/PolyMC/releases');
+  const versions = await f.json();
+  cachedVer = versions[0].tag_name;
+  cachedTimestamp = Date.now();
+  return versions[0].tag_name;
+}