otel-js website_docs at HEAD

[chalin]

Contributes to #720.

This PR has two commits:

• The first copies the content, as is, of https://github.com/open-telemetry/opentelemetry-js/tree/main/website_docs at the current otel-js HEAD, which is open-telemetry/opentelemetry-js@feea516
• Then fixes the broken links to exporters

The end result is mainly the update of open-telemetry/opentelemetry-js#2421, but there are other changes -- I don't know where those come from. Somehow the docs drifted?

cc @open-telemetry/javascript-maintainers

If y'all agree to this PR, we'll merge this first, then (i) delete the website_docs on the otel-js side, (ii) update the index page here to remove the cascaded values of github_repo etc.

[austinlparker]

lgtm with the links restored