Support international domain names in lists (IDNA)

[ThinkChaos]

See #960

Example list: https://raw.githubusercontent.com/rahilpathan/pihole-whitelist/main/1.LowWL.txt
Fix idea: use the idna module's ToASCII to convert those domains to their punycode representation which is what blocky should receive from clients.

[0xERR0R]

I changed it from bug to feature 😄

We support currently lists in hosts file format or plain domain names. A particular domain name may contain only letters, numbers (and some special characters like hyphen). List maintainers should validate its content and use only valid names.

It is a very good idea to convert list content on-the-fly to punycode if necessary. Since user can also create his own lists or use inline definitions. 👍