docs(prometheus/scrape): add example for K8s auth (#829) (#844)

* docs(prometheus/scrape): add example for K8s auth

Signed-off-by: hainenber <dotronghai96@gmail.com>

* Apply suggestions from Clayton's code review

Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

* Apply suggestions from 2nd Clayton's code review

Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

---------

Signed-off-by: hainenber <dotronghai96@gmail.com>
Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>
(cherry picked from commit d8831a5)

Co-authored-by: Đỗ Trọng Hải <41283691+hainenber@users.noreply.github.com>

docs/sources/reference/components/prometheus.scrape.md

@@ -259,6 +259,8 @@ present.
 
 ## Example
 
+### Set up scrape jobs for `blackbox exporter` targets  
+
 The following example sets up the scrape job with certain attributes (scrape
 endpoint, scrape interval, query parameters) and lets it scrape two instances
 of the [blackbox exporter](https://github.com/prometheus/blackbox_exporter/).
@@ -286,6 +288,22 @@ http://blackbox-exporter:9115/probe?target=grafana.com&module=http_2xx
 http://blackbox-exporter:9116/probe?target=grafana.com&module=http_2xx
 ```
 
+### Authentication with the Kubernetes API server
+
+The following example shows you how to authenticate with the Kubernetes API server.
+
+```alloy
+prometheus.scrape "kubelet" {
+        scheme = "https"
+        tls_config {
+            server_name = "kubernetes"
+            ca_file = "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt"
+            insecure_skip_verify = false
+        }
+        bearer_token_file = "/var/run/secrets/kubernetes.io/serviceaccount/token"
+}
+```
+
 ### Technical details
 
 `prometheus.scrape` supports [gzip](https://en.wikipedia.org/wiki/Gzip) compression.