Learn OpenTelemetry: New Getting Started & Best Practices

[svrnm]

This is a follow up to #4475 and a prototype for what I have described in this document.

To begin with, please ignore the implementation details and let's talk about the outcome, i.e. is this how we can move forward with providing a better "Getting Started" for OpenTelemetry.

Preview: https://deploy-preview-5376--opentelemetry.netlify.app/docs/learn/getting-started/

I see a few advantages in this approach:

• We remove the "Dev/Ops" Getting Started and replace it with a single (developer oriented) guide, that's focusing on natively instrumenting your application using the API&SDK, which is in line with our project's mission.
• We untangle a problem that we have been facing since we tried to have more consistent documentation across languages: we mix opinionated guides with technical references. Together with @jack-berg's work (see Refactor java SDK and configuration #4966 and Refactor java instrumentation #5276) we separate the 2 much more.
• We have a dedicated place that also allows us to have "Tutorials" (as suggested by @avillela), such that users can add some step by step guides to our documentation at a single place.
• With externalizing the example code to the language repositories + using code excerpts, we have a kind of "reference application" that showcases features per language consistently.

[jack-berg]

Very cool idea! Love the dropdown to toggle between different language options. Really hammers home the point that opentelemetry is a language agnostic toolkit.