refactor: use ValueTask over Task where appropriate (#710)

Author: JamieMagee

README.md

@@ -17,7 +17,7 @@ Libraries to handle GitHub Webhooks in .NET applications.
     ```C#
     public sealed class MyWebhookEventProcessor : WebhookEventProcessor
     {
-        protected override Task ProcessPullRequestWebhookAsync(
+        protected override ValueTask ProcessPullRequestWebhookAsync(
             WebhookHeaders headers,
             PullRequestEvent pullRequestEvent,
             PullRequestAction action,
@@ -60,7 +60,7 @@ Libraries to handle GitHub Webhooks in .NET applications.
     ```C#
     public sealed class MyWebhookEventProcessor : WebhookEventProcessor
     {
-        protected override Task ProcessPullRequestWebhookAsync(
+        protected override ValueTask ProcessPullRequestWebhookAsync(
             WebhookHeaders headers,
             PullRequestEvent pullRequestEvent,
             PullRequestAction action,

samples/AspNetCore/MyWebhookEventProcessor.cs

@@ -9,7 +9,7 @@ namespace AspNetCore;
 
 public class MyWebhookEventProcessor(ILogger<MyWebhookEventProcessor> logger) : WebhookEventProcessor
 {
-    protected override async Task ProcessPullRequestWebhookAsync(
+    protected override async ValueTask ProcessPullRequestWebhookAsync(
         WebhookHeaders headers,
         PullRequestEvent pullRequestEvent,
         PullRequestAction action,

samples/AzureFunctions/MyWebhookEventProcessor.cs

@@ -9,7 +9,7 @@ namespace AzureFunctions;
 
 public class MyWebhookEventProcessor(ILogger<MyWebhookEventProcessor> logger) : WebhookEventProcessor
 {
-    protected override async Task ProcessPullRequestWebhookAsync(
+    protected override async ValueTask ProcessPullRequestWebhookAsync(
         WebhookHeaders headers,
         PullRequestEvent pullRequestEvent,
         PullRequestAction action,