loki_out: add structured_metadata_map docs

[0x006EA1E5]

Adds docs for PR fluent/fluent-bit#9530

[cnorris-cs]

I left suggestions, but I've added my approval based on that to keep this moving.

[patrick-stephens]

Can we do the tabs for YAML and TOML config so we have examples of both?

[patrick-stephens]

fluent-bit-docs/pipeline/outputs/dash0.md

Lines 32 to 60 in e9429f3

	{% tabs %}
	{% tab title="fluent-bit.conf" %}
	```text
	[OUTPUT]
	Name opentelemetry
	Match *
	Host ingress.eu-west-1.aws.dash0.com
	Port 443
	Header Authorization Bearer {your-Auth-token-here}
	Metrics_uri /v1/metrics
	Logs_uri /v1/logs
	Traces_uri /v1/traces
	```
	{% endtab %}
	{% tab title="fluent-bit.yaml" %}
	```yaml
	[OUTPUT]
	Name: opentelemetry
	Match: *
	Host: ingress.eu-west-1.aws.dash0.com
	Port: 443
	Header: Authorization Bearer {your-Auth-token-here}
	Metrics_uri: /v1/metrics
	Logs_uri: /v1/logs
	Traces_uri: /v1/traces
	```
	{% endtab %}
	{% endtabs %}