feat: expose the tzdb version of the bundled zonefile

scripts/tz/update.js

@@ -187,7 +187,7 @@ export const main = (args = process.argv.slice(2)) => {
     tzdata: version,
     unsupported: unsupported.map((o) => o.name)
   })
-  const text = `// Generated by scripts/tz/update.js: ${source}\nexport default ${JSON.stringify(result, null, 2)}\n`
+  const text = `// Generated by scripts/tz/update.js: ${source}\nexport const tzdbVersion = ${JSON.stringify(version)}\nexport default ${JSON.stringify(result, null, 2)}\n`
   // Rename within the destination directory so readers never see a partial file.
   // Only remove a temporary file created by this run (exclusive creation may fail).
   const temporary = join(dirname(options.output), `.zonefile-${process.pid}.tmp`)