fix: Add getting started documentation.

Author: goloroden

README.md

@@ -1,3 +1,34 @@
 # eventsourcingdb
 
-The official JavaScript client SDK for EventSourcingDB.
+The official JavaScript client SDK for [EventSourcingDB](https://www.eventsourcingdb.io) – a purpose-built database for event sourcing.
+
+EventSourcingDB enables you to build and operate event-driven applications with native support for writing, reading, and observing events. This client SDK provides convenient access to its capabilities in JavaScript and TypeScript.
+
+For more information on EventSourcingDB, see its [official documentation](https://docs.eventsourcingdb.io/).
+
+## Getting Started
+
+Import the `Client` class and create an instance by providing the URL of your EventSourcingDB instance and the API token to use:
+
+```typescript
+import { Client } from 'eventsourcingdb';
+
+const url = new URL('http://localhost:3000');
+const apiToken = 'secret';
+
+const client = new Client(url, apiToken);
+```
+
+Then call the `ping` function to check whether the instance is reachable. If it is not, the function will throw an error:
+
+```typescript
+await client.ping();
+```
+
+*Note that `ping` does not require authentication, so the call may succeed even if the API token is invalid.*
+
+If you want to verify the API token, call `verifyApiToken`. If the token is invalid, the function will throw an error:
+
+```typescript
+await client.verifyApiToken();
+```