span connector output readme update

[vikashkumar2020]

Description

Added output of span metric connector into the readme based on the given example.

Link to tracking issue

Fixes Issue

Testing

Used sample go application to generate the spans. Then below otel config used for get spanmetrics metrics into prometheus.

receivers:
  otlp:
    protocols:
      http:
        endpoint: 0.0.0.0:4318
      grpc:
        endpoint: 0.0.0.0:4317

processors:
  batch:
    timeout: 10s
    send_batch_size: 1000

exporters:
  prometheusremotewrite:
    endpoint: "http://prometheus:9090/api/v1/write"
    tls:
      insecure: true
    target_info:
      enabled: true

  debug:
    verbosity: detailed

connectors:
  spanmetrics:
    histogram:
      explicit:
        buckets: [100us, 1ms, 2ms, 6ms, 10ms, 100ms, 250ms]
    dimensions:
      - name: http.method
        default: GET
      - name: http.status_code
    exemplars:
      enabled: true
    exclude_dimensions: ['status.code']
    dimensions_cache_size: 1000
    aggregation_temporality: "AGGREGATION_TEMPORALITY_CUMULATIVE"
    metrics_flush_interval: 15s
    metrics_expiration: 5m
    events:
      enabled: true
      dimensions:
        - name: exception.type
        - name: exception.message
    resource_metrics_key_attributes:
      - service.name
      - telemetry.sdk.language
      - telemetry.sdk.name

service:
  pipelines:
    traces:
      receivers: [otlp]
      processors: [batch]
      exporters: [spanmetrics]
    metrics:
      receivers: [spanmetrics]
      processors: [batch]
      exporters: [prometheusremotewrite, debug]

  telemetry:
    logs:
      level: debug

Documentation

Updated the readme

[dehaansa]

It's not clear, is this meant to be attached to the example above it? The markdown headers do not make it very clear, and this could use some more descriptive sentences/paragraphs outlining what exactly you're documenting.

[vikashkumar2020]

@dehaansa Addressed the concern changes

[dehaansa]

I'm not sure that this addition is valuable in its current form. A much more concise addition of example metrics at the end of each example configuration would likely add the value that the raised issue is seeking.

[dehaansa]

This reads like an AI-generated summary, and doesn't belong in this section.

[dehaansa]

This assumes the configuration being used is exporting to prometheus, and that it's a local prometheus. Should this output metrics section belong to one of the examples above instead of being in its own section?

[dehaansa]

The metrics generated are not prometheus-formatted, they are opentelemetry metrics that in your example are exported to a prometheus endpoint using the exporter.

[dehaansa]

These are already listed at the end of the Overview section, and also can be disabled using the exclude_dimensions configuration parameter.

[dehaansa]

This is only true in your example that exports to prometheus.