Add logback configuration doc
See
ADD
instrumentation/logback/logback-appender-1.0/javaagent/README.md
+# Settings for the Logback Appender instrumentation
+
+| System property | Type | Default | Description |
+|---|---------|--|------------------------------------------------------|
+| `otel.instrumentation.logback-appender.experimental-log-attributes` | Boolean | `false` | Enable the capture of experimental span attributes `thread.name` and `thread.id`. |
+| `otel.instrumentation.logback-appender.experimental.capture-code-attributes` | Boolean | `false` | Enable the capture of [source code attributes]. Note that capturing source code attributes at logging sites might add a performance overhead. |
+| `otel.instrumentation.logback-appender.experimental.capture-marker-attribute` | Boolean | `false` | Enable the capture of Logback markers as attributes. |
+| `otel.instrumentation.logback-appender.experimental.capture-mdc-attributes` | String | | List of MDC attributes to capture. Use the wildcard character `*` to capture all attributes. |
+
+[source code attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/span-general.md#source-code-attributes

Add logback configuration doc (#7392)

See #7389

Co-authored-by: Fabrizio Ferri-Benedetti <fferribenedetti@splunk.com>