docs: note mask-client-id and max-context-population are available in azure/login@v3

Add an 'Available in azure/login@v3' label under each input heading. Both
are v3-only inputs (not present in v2), so this documents the version and
points consumers at v3.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: MaddyMicrosoft

README.md

@@ -176,6 +176,8 @@ Refer to [Login With OpenID Connect (OIDC)](#login-with-openid-connect-oidc-reco
 
 ### `mask-client-id`
 
+_Available in `azure/login@v3`._
+
 The input parameter `mask-client-id` controls whether the login client id is registered as a secret and masked in the workflow logs. It defaults to `true`.
 
 Set it to `false` when the client id is not treated as sensitive and masking gets in the way, for example when the same value appears in log output or command results that you need to read.
@@ -272,6 +274,8 @@ Refer to [Login With System-assigned Managed Identity](#login-with-system-assign
 
 ### `max-context-population`
 
+_Available in `azure/login@v3`._
+
 The input parameter `max-context-population` is only used when [`enable-AzPSSession`](#enable-azpssession) is `true`. It overrides the Azure PowerShell `MaxContextPopulation` value that `Connect-AzAccount` uses, which controls how many subscription contexts are loaded into the session.
 
 Azure PowerShell loads a maximum of 25 subscription contexts by default. When the identity has access to more than 25 subscriptions, only a subset is loaded, so commands that enumerate or target subscriptions outside that subset may behave inconsistently. Set `max-context-population` to `-1` to load all subscriptions, or to a positive integer (1 to 2147483647) to load a specific number. When it is unset, the Azure PowerShell default of 25 applies and behavior is unchanged.