Add Errors Inbox metadata configuration content to generated doc

[kaylareopelle]

The Errors Inbox team would like the Ruby agent's configuration document to include the following:

## Errors inbox configuration [#errors-inbox-configuration]

Setting one of the following environment variables will help you identify which versions of your software are producing the errors. 

* `NEW_RELIC_METADATA_SERVICE_VERSION` will create tags.service.version on event data containing the version of your code that is deployed, in many cases a semantic version such as 1.2.3, but not always.
* `NEW_RELIC_METADATA_RELEASE_TAG ` will create tags.releaseTag on event data containing the release tag (such as v0.1.209 or release-209).  
* `NEW_RELIC_METADATA_COMMIT` will create tags.commit on event data containing the commit sha. The entire sha can be used or just the first seven characters (e.g., 734713b). 

[Errors inbox](https://docs.newrelic.com/docs/errors-inbox/version-tracking/) will automatically track which versions of your software are producing errors. Any version data will also be displayed in [CodeStream](/docs/codestream/how-use-codestream/performance-monitoring/#buildsha). 

These features have been verified to work on a Rails 7 application: (permalink/internal)

This documentation was manually added to our configuration doc, and overridden by our generator.

Our current generator uses the configs defined in our lib/new_relic/agent/configuration/default_source.rb file to generate sections. These configs are not defined in our default_source.rb file. Consider whether we want to add them to default_source.rb or add this section in another way.

[workato-integration]

https://new-relic.atlassian.net/browse/NR-279222

[meda123]

@kaylareopelle - Thanks so much for adding this to your docs. Could we change "An upcoming release of errors inbox" to "Errors inbox will automatically..." because we've already launched the version tracking update :), it's no longer an upcoming release.

[kaylareopelle]

@meda123, great catch! I updated the text in the description to include your edit. 🙂

I also updated tags to environment variables in the sentence, Setting one of the following environment variables...

Does that work for you?