Add dns.txt to DB dir after update
Add dns.txt to DB dir after update

Generate the dns.txt file like the old `clamdownloader.pl` script.
This file is written to the database directory whenever an update
updates 1+ databases with 0 errors.

This addresses Issue #2

The format should match the original:

❯ bat ~/.cvdupdate/database/dns.txt
───────┬─────────────────────────────────────────────────────────────
       │ File: /home/micasnyd/.cvdupdate/database/dns.txt
───────┼─────────────────────────────────────────────────────────────
   1   │ 0.103.1:59:26104:1615408140:0:63:49191:333
───────┴─────────────────────────────────────────────────────────────

micahsnyder/cvdupdate