migrate to "export default"

also, set no-use-before-define in linter

src/ipaddr.js

@@ -1,12 +1,6 @@
 import assert from 'node:assert';
 import net from 'node:net';
 
-export {
-    isValid,
-    isValidCIDR,
-    isEqual,
-    includes,
-};
 
 function isValid(ip) {
     assert.strictEqual(typeof ip, 'string');
@@ -58,3 +52,10 @@ function includes(cidr, ip) {
     blockList.addSubnet(subnet, parseInt(prefix, 10), `ipv${subnetType}`);
     return blockList.check(ip, `ipv${type}`);
 }
+
+export default {
+    isValid,
+    isValidCIDR,
+    isEqual,
+    includes,
+};