docs: add spanish readme

Author: javorosas

README.es.md

@@ -0,0 +1,106 @@
+# facturapi-java
+
+SDK oficial de Java para [Facturapi](https://www.facturapi.io).
+
+English: [README.md](README.md)
+
+[![CI](https://img.shields.io/github/actions/workflow/status/facturapi/facturapi-java/ci.yml?branch=main&style=for-the-badge&label=CI)](https://github.com/facturapi/facturapi-java/actions/workflows/ci.yml)
+[![Maven Central](https://img.shields.io/maven-central/v/io.facturapi/facturapi-java?style=for-the-badge&label=Maven%20Central)](https://central.sonatype.com/artifact/io.facturapi/facturapi-java)
+[![Java](https://img.shields.io/badge/Java-11%2B-ED8B00?style=for-the-badge&logo=openjdk&logoColor=white)](https://openjdk.org/)
+
+## Requisitos
+
+- Java 11+
+- Kotlin/JVM
+- Android 8.0 (API level 26) o superior
+- Spring Boot, Jakarta EE, Quarkus, Micronaut y otras apps JVM de servidor
+
+## Instalación
+
+Maven:
+
+```xml
+<dependency>
+  <groupId>io.facturapi</groupId>
+  <artifactId>facturapi-java</artifactId>
+  <version>0.1.0</version>
+</dependency>
+```
+
+Gradle:
+
+```gradle
+implementation("io.facturapi:facturapi-java:0.1.0")
+```
+
+## Inicio rápido
+
+```java
+import io.facturapi.Facturapi;
+import java.util.Map;
+
+Facturapi facturapi = new Facturapi("sk_test_...");
+
+var customer = facturapi.customers().create(Map.of(
+  "legal_name", "Mi Empresa SA de CV",
+  "tax_id", "XAXX010101000",
+  "tax_system", "601",
+  "email", "cliente@example.com"
+), null);
+
+var invoice = facturapi.invoices().create(Map.of(
+  "customer", customer.getId(),
+  "items", java.util.List.of(Map.of("quantity", 1, "product", "prod_123"))
+), null);
+
+System.out.println(invoice.getId());
+```
+
+## Subidas
+
+```java
+import java.io.File;
+
+var organization = facturapi.organizations().uploadLogo(
+  "org_123",
+  new File("logo.png")
+);
+
+var updated = facturapi.organizations().uploadCertificate(
+  "org_123",
+  new File("certificate.cer"),
+  new File("certificate.key"),
+  "secret"
+);
+```
+
+## Errores
+
+```java
+import io.facturapi.FacturapiException;
+
+try {
+  facturapi.customers().retrieve("cus_123");
+} catch (FacturapiException e) {
+  System.out.println(e.getMessage());
+  System.out.println(e.getStatusCode());
+  System.out.println(e.getErrorCode());
+  System.out.println(e.getErrorPath());
+}
+```
+
+## Diseño
+
+- Las entradas usan diccionarios JSON flexibles (`Map<String, Object>`).
+- Las salidas son modelos Java tipados (`Invoice`, `Customer`, `SearchResult<T>`, etc.).
+- Los errores exponen directamente los campos útiles del error del API en `FacturapiException`.
+- La autenticación usa `Authorization: Bearer <apiKey>`.
+
+## Configuración
+
+```java
+Facturapi facturapi = Facturapi.builder("sk_test_...")
+  .apiVersion("v2")
+  .timeout(java.time.Duration.ofSeconds(20))
+  .build();
+```

README.md

@@ -2,6 +2,8 @@
 
 Official Java SDK for [Facturapi](https://www.facturapi.io).
 
+Español: [README.es.md](README.es.md)
+
 [![CI](https://img.shields.io/github/actions/workflow/status/facturapi/facturapi-java/ci.yml?branch=main&style=for-the-badge&label=CI)](https://github.com/facturapi/facturapi-java/actions/workflows/ci.yml)
 [![Maven Central](https://img.shields.io/maven-central/v/io.facturapi/facturapi-java?style=for-the-badge&label=Maven%20Central)](https://central.sonatype.com/artifact/io.facturapi/facturapi-java)
 [![Java](https://img.shields.io/badge/Java-11%2B-ED8B00?style=for-the-badge&logo=openjdk&logoColor=white)](https://openjdk.org/)