Feat: legacy Clash Premium support

Build/lib/writing-strategy/legacy-clash-premium.ts

@@ -0,0 +1,18 @@
+import { noop } from 'foxts/noop';
+import { OUTPUT_LEAGCY_CLASH_PREMIUM } from '../../constants/dir';
+import { ClashClassicRuleSet } from './clash';
+
+export class LegacyClashPremiumRuleSet extends ClashClassicRuleSet {
+  public override readonly name = 'legacy clash premium ruleset';
+
+  readonly fileExtension = 'txt';
+
+  protected result: string[] = ['DOMAIN,this_ruleset_is_made_by_sukkaw.ruleset.skk.moe'];
+
+  constructor(public readonly type: 'ip' | 'non_ip' /* | (string & {}) */, public readonly outputDir = OUTPUT_LEAGCY_CLASH_PREMIUM) {
+    super(type, outputDir);
+  }
+
+  override writeDomainWildcards = noop;
+  override writeIpAsns = noop;
+}