Support Auth extension

[vprivat-ads]

It would be great to have authentication support in stac-cli, just like stac-browser is doing with radiantearth/stac-browser#81 and https://github.com/radiantearth/stac-browser/blob/main/docs/options.md#authconfig

For example, to access an API Key protected STAC instance, I'd like to do something that would like this:

stac search --auth-type=apiKey --auth-in=header --auth-name=x-api-key <HREF>

[gadomski]

For this example:

stac search --auth-type=apiKey --auth-in=header --auth-name=x-api-key <HREF>

How would you want to supply to key itself? Environment variable?

[vprivat-ads]

I would be fine with any solution. I could imagine passing it on the command line, use an environment variable, or having to enter it interactively in the terminal.