Get STAC browser to work with authentication enabled

[batpad]

Now that we can configure stac-auth-proxy as an optional dependency to enable authentication: #358 , it would be cool if the bundled STAC browser could be configured to work with the authentication scheme.

Stubbing out the ticket - I'll look into this more and write out details - from testing this out earlier, one needed to add a custom authConfig.js to the STAC browser, so we'll need to figure making a custom build of the STAC browser with that config.

Just making a ticket so it's not forgotten - it would be cool if this could work out of the box. Am happy to look into it.

cc @pantierra

[batpad]

Note to self: this is where the stac-browser custom image is being built: https://github.com/developmentseed/eoapi-k8s/blob/main/.github/workflows/stac-browser.yml#L66

This is the docs to configure authConfig for the STAC browser: https://github.com/radiantearth/stac-browser/blob/main/docs/options.md#authconfig

Still not sure the best approach for this as it seems like it will require us to add the authConfig at build time - I'll play around a bit with config locally and see if there's an approach that seems to make sense.