getting started docs

[trentm]

• intro
• configuration
• setup/starting the SDK
• ESM page
• troubleshooting
• changelog (aka Release Notes)
• migration guide from elastic-apm-node

[david-luna]

As discussed we will start with plain markdown files. This task could be started once we have a 1st draft/PoC of #1 and we have figured out:

• require/import node options usage
• advanced bootstrap using the wrapper in a js|ts file
• configuration sources: env, file, start, ...? (to be discussed in configuration plan: separate or share config with the non-OTel elastic agents #3 )

[trentm]

For ref here is the Java distro equiv: elastic/elastic-otel-java#25