Implement product feedback to readme (#15261)

* remove mentions of nvidia devs

* Describe how to add extra metrics

dcgm/README.md

@@ -29,7 +29,7 @@ DCGM_FI_PROF_PCIE_TX_BYTES,              counter, Total number of bytes transmit
 DCGM_FI_PROF_PCIE_RX_BYTES,              counter, Total number of bytes received through PCIe RX (in KB) via NVML.
 ```
 
-NVIDIA devs also recommend enabling the following default counters and labels:
+It is also recommended enabling the following default counters and labels:
 - `DCGM_FI_DEV_MEMORY_TEMP`
 - `DCGM_FI_DEV_GPU_TEMP`
 - `DCGM_FI_DEV_POWER_USAGE`
@@ -43,7 +43,7 @@ NVIDIA devs also recommend enabling the following default counters and labels:
 - `DCGM_FI_DEV_BRAND`
 - `DCGM_FI_DEV_SERIAL`
 
-They also recommend adding the following non-default fields and labels:
+The following non-default fields and labels are also recommended:
 ```
 DCGM_FI_DEV_SLOWDOWN_TEMP,              gauge, Slowdown temperature for the device.
 DCGM_FI_DEV_POWER_MGMT_LIMIT,           gauge, Current power limit for the device.
@@ -107,6 +107,8 @@ instances:
     - openmetrics_endpoint: http://localhost:9400/metrics
 ```
 
+Use the `extra_metrics` configuration field to add metrics that go beyond the ones [we support out of the box][6]. See [here][10] for the full list of metrics that dcgm-exporter can collect. Make sure to [enable these fields in the dcgm-exporter configuration][9] as well.
+
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