feat: accept --networks as an alias of --network

[ScreamingHawk]

This PR prevents my own idiocy...

--networks now works anywhere --network does (run, dry-run, etherscan). Typing the plural is too easy.

mapAliases in src/index.ts rewrites aliased long flags in argv before commander parses them, covering both --networks x and --networks=x. Commander 11 can't give a long option a second name, so this is the smallest way to do it. Adding another alias is one entry in OPTION_ALIASES.

Things to watch:

• The alias is hidden: --help only shows --network.
• The rewrite runs on all of argv, so an option value that is literally --networks gets rewritten too.

[miguelmota]

LGTM!