docs: improve go docs by adding a readme

[amoeba]

Improves the existing go pkgsite by adding a README.

This is an alternative to #3199.

[amoeba]

I deployed a preview to https://6883d84fdd2114b798da2f70--adbc-docs.netlify.app if anyone wants to take a look. I think this is pretty promising as a way of achieving #3198 without abandoning the built-in Go pkgsite documentation tool.

[zeroshade]

just some nit picks!

[amoeba]

Thanks for the reviews.

After creating this PR, I found out you can do some degree of package-level documentation in source code headers and also in standalone doc.go files but you're limited to only a single heading level which I don't think is ideal. I'm going to keep going with the README.md approach since it seems to work and address the feedback.

[amoeba]

I addressed a number of the comments around my incorrect/imprecise language by avoiding it altogether since it wasn't critical. I tested the code by extracting it into a test package (awk command included in README) so I feel pretty good about it now.

@zeroshade can you give this a +1 if you like the direction?

[zeroshade]

Just a couple nitpicks, but otherwise +1 from me!

[amoeba]

Merged, thanks for the reviews.