feat: add documentation for metric-scaler-format

Signed-off-by: Friedrich Albert Kyuri <friedrichak42@gmail.com>

content/docs/2.14/scalers/metrics-api.md

@@ -19,6 +19,7 @@ triggers:
 - type: metrics-api
   metadata:
     targetValue: "8.8"
+    format: "json"
     activationTargetValue: "3.8"
     url: "http://api:3232/api/v1/stats"
     valueLocation: "components.worker.tasks"
@@ -27,7 +28,10 @@ triggers:
 **Parameter list:**
 
 - `url` - Full URL of the API operation to call to get the metric value (eg. `http://app:1317/api/v1/stats`).
-- `valueLocation` - [GJSON path notation](https://github.com/tidwall/gjson#path-syntax) to refer to the field in the payload containing the metric value.
+- `format` - One of the following formats: `json`, `xml`, `yaml`, `prometheus`. (Default: `json`, Optional)
+- `valueLocation` - The location of the metric value in the response payload. The value is format specific.
+  * `json` - [GJSON path notation](https://github.com/tidwall/gjson#path-syntax) to refer to the field in the payload containing the metric value.
+  * `yaml`, `xml`, `prometheus` - We use internal implementation that retrieves a value using a dot-separated path: [#2633](https://github.com/kedacore/keda/issues/2633).
 - `targetValue` - Target value to scale on. When the metric provided by the API is equal or higher to this value, KEDA will start scaling out. When the metric is 0 or less, KEDA will scale down to 0. (This value can be a float)
 - `activationTargetValue` - Target value for activating the scaler. Learn more about activation [here](./../concepts/scaling-deployments.md#activating-and-scaling-thresholds).(Default: `0`, Optional, This value can be a float)
 - `unsafeSsl` - Skip certificate validation when connecting over HTTPS. (Values: `true`, `false`, Default: `false`, Optional)