Use function pattern matching to solve naming issues

[nappex]

If we use function pattern matching feature available in elixir then we can use same name for some functions in Downloader module.

Consider to rename main as download and download_urls_from_file also as download then these will diff just by defined arguments. Download without any args will behave as our main and download with defined arg as only one a needs to be file will behave as our download_urls_from_file. This approach will solve our naming issue.

function pattern matching - https://inquisitivedeveloper.com/lwm-elixir-23/