add authentication support for private repositories

[ehthxC7x9D]

support for ~/.netrc
support for environment variable
support for stdin

notes:

I was not able to confirm that wget, independent of vet, could read my ~/.netrc file despite it being used successfully by curl. I was testing on wget 1.21.3 debian bookworm, so maybe someone else can verify that please.

re: issue #4

[lykhvar]

@jarebear6expepjozn6rakjq5iczi3irqwphcvb, thank you for this contribution! My apologies for the delayed response; it’s been a busy few days. I’ll be reviewing it over the next couple of days and am excited to dig in.

[lykhvar]

Thanks again for this PR @jarebear6expepjozn6rakjq5iczi3irqwphcvb! Your work here was a huge help, as it made me realize the original specification for this feature needs to be extended.

Rather than merging directly, my plan is to retarget this PR to a new feature branch. From there, I’ll build on your work, introduce a custom HTTP header option, update the test cases, and then merge into main with you credited as co-author.

Thanks again for taking the time to contribute and get this feature started!