docs: Add Elasticsearch example

docs/modules/elasticsearch.md

@@ -0,0 +1,59 @@
+# Elasticsearch
+
+[Elasticsearch](https://www.elastic.co/elasticsearch/) is a distributed, RESTful search and analytics engine capable of addressing a growing number of use cases. As the heart of the Elastic Stack, it centrally stores data for lightning fast search, fine‑tuned relevancy, and powerful analytics that scale with ease.
+
+The following example uses the following NuGet packages:
+
+```console title="Install the NuGet dependencies"
+dotnet add package Testcontainers.Elasticsearch
+dotnet add package Elastic.Clients.Elasticsearch
+dotnet add package xunit
+```
+
+IDEs and editors may also require the following packages to run tests: `xunit.runner.visualstudio` and `Microsoft.NET.Test.Sdk`.
+
+Copy and paste the following code into a new `.cs` test file within an existing test project.
+
+```csharp
+using Elastic.Clients.Elasticsearch;
+using Elastic.Transport;
+using Testcontainers.Elasticsearch;
+using Xunit;
+
+namespace TestcontainersModules;
+
+public class ElasticsearchContainerTest : IAsyncLifetime
+{
+    private readonly ElasticsearchContainer elasticsearch
+        = new ElasticsearchBuilder()
+            .Build();
+
+    [Fact]
+    public async Task ReadFromElasticsearch()
+    {
+        var connectionString = elasticsearch.GetConnectionString();
+        var settings = new ElasticsearchClientSettings(new Uri(connectionString));
+        settings.ServerCertificateValidationCallback(CertificateValidations.AllowAll);
+
+        var client = new ElasticsearchClient(settings);
+
+        var stats = await client.PingAsync();
+
+        Assert.True(stats.IsValidResponse);
+    }
+
+    public Task InitializeAsync()
+        => elasticsearch.StartAsync();
+
+    public Task DisposeAsync()
+        => elasticsearch.DisposeAsync().AsTask();
+}
+```
+
+To execute the tests, use the command `dotnet test` from a terminal.
+
+## A Note To Developers
+
+The Testcontainers module creates a container that listens to requests over **HTTPS**. To communicate with the Elasticsearch instance, developers must create a `ElasticsearchClientSettings` instance and set the `ServerCertificateValidationCallback` delegate to `CertificateValidations.AllowAll`. Failing to do so will result in a communication failure as the .NET will reject the certificate coming from the container.
+
+[xunit]: https://xunit.net/