update wiki pages

CHANGELOG.md

@@ -28,6 +28,7 @@ The sandbox cluster installation is running under the constant load generated by
 
 ## tip
 
+* FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): expose ability to set additional endpoint parameters when requesting an OAuth2 token via a the flag `remoteWrite.oauth2.endpointParams`. See [these docs](https://docs.victoriametrics.com/vmagent.html#advanced-usage).
 * FEATURE: [vmauth](https://docs.victoriametrics.com/vmauth.html): add ability to proxy incoming requests to different backends based on the requested host via `src_hosts` option at `url_map`. See [these docs](https://docs.victoriametrics.com/vmauth.html#generic-http-proxy-for-different-backends).
 * FEATURE: [vmctl](https://docs.victoriametrics.com/vmctl.html): rename cmd-line flag `vm-native-disable-retries` to `vm-native-disable-per-metric-migration` to better reflect its meaning.
 * FEATURE: all VictoriaMetrics components: add ability to specify arbitrary HTTP headers to send with every request to `-pushmetrics.url`. See [`push metrics` docs](https://docs.victoriametrics.com/#push-metrics).

vmagent.md

@@ -1921,6 +1921,9 @@ See the docs at https://docs.victoriametrics.com/vmagent.html .
   -remoteWrite.oauth2.clientSecretFile array
      Optional OAuth2 clientSecretFile to use for the corresponding -remoteWrite.url
      Supports an array of values separated by comma or specified via multiple flags.
+  -remoteWrite.oauth2.endpointParams array
+     Optional OAuth2 endpointParams to use for the corresponding -remoteWrite.url. Keys and values must be seperated by ':'.
+     Supports and array of key:value pairs seperated by comma or specified via multiple flags.
   -remoteWrite.oauth2.scopes array
      Optional OAuth2 scopes to use for the corresponding -remoteWrite.url. Scopes must be delimited by ';'
      Supports an array of values separated by comma or specified via multiple flags.