feat(block-kit): add data table block example

Add a DataTable block-kit example (blocks/DataTable.java) demonstrating a
data_table block with raw_text, raw_number, and rich_text-capable cells,
plus a DataTableTest round-trip test and a README entry.

Depends on the DataTableBlock / TableCell model added in
slackapi/java-slack-sdk#1613 (not yet released); the block-kit module
pins the published slack-api-model, so this compiles once that lands.

Co-Authored-By: Claude <svc-devxp-claude@slack-corp.com>

Author: zimeg

block-kit/README.md

@@ -13,6 +13,7 @@ Read the [docs](https://docs.slack.dev/block-kit/) to learn concepts behind thes
 - **[Carousel](https://docs.slack.dev/reference/block-kit/blocks/carousel-block)**: Displays related card blocks in a horizontally-scrolling container. [Implementation](./src/main/java/blocks/Carousel.java).
 - **[Card](https://docs.slack.dev/reference/block-kit/blocks/card-block)**: Displays content in a card. [Implementation](./src/main/java/blocks/Card.java).
 - **[Context](https://docs.slack.dev/reference/block-kit/blocks/context-block)**: Provides contextual info, which can include both images and text. [Implementation](./src/main/java/blocks/Context.java).
+- **[Data table](https://docs.slack.dev/reference/block-kit/blocks/data-table-block)**: Displays rich tables that support pagination, sorting, filtering, and interactivity. [Implementation](./src/main/java/blocks/DataTable.java).
 - **[Divider](https://docs.slack.dev/reference/block-kit/blocks/divider-block)**: Visually separates pieces of info inside of a message. [Implementation](./src/main/java/blocks/Divider.java).
 - **[File](https://docs.slack.dev/reference/block-kit/blocks/file-block)**: Displays info about remote files. [Implementation](./src/main/java/blocks/File.java).
 - **[Header](https://docs.slack.dev/reference/block-kit/blocks/header-block)**: Displays a larger-sized text. [Implementation](./src/main/java/blocks/Header.java).

block-kit/src/main/java/blocks/DataTable.java

@@ -0,0 +1,33 @@
+package blocks;
+
+import com.slack.api.model.block.Blocks;
+import com.slack.api.model.block.DataTableBlock;
+import com.slack.api.model.block.composition.RawNumberObject;
+import com.slack.api.model.block.composition.RawTextObject;
+import java.util.List;
+
+/**
+ * Displays rich tables that support pagination, sorting, filtering, and interactivity.
+ * {@link https://docs.slack.dev/reference/block-kit/blocks/data-table-block/}
+ */
+public class DataTable {
+    /**
+     * A data table pairing text labels with numeric values.
+     */
+    public static DataTableBlock example01() {
+        DataTableBlock block = Blocks.dataTable(t -> t.caption("Quarterly widget report")
+                .pageSize(10)
+                .rowHeaderColumnIndex(0)
+                .rows(List.of(
+                        List.of(
+                                RawTextObject.builder().text("Item").build(),
+                                RawTextObject.builder().text("Count").build()),
+                        List.of(
+                                RawTextObject.builder().text("Widgets").build(),
+                                RawNumberObject.builder().value(42.0).text("42").build()),
+                        List.of(
+                                RawTextObject.builder().text("Gadgets").build(),
+                                RawNumberObject.builder().value(7.0).text("7").build()))));
+        return block;
+    }
+}

block-kit/src/test/java/blocks/DataTableTest.java

@@ -0,0 +1,39 @@
+package blocks;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import com.google.gson.JsonParser;
+import com.slack.api.model.block.DataTableBlock;
+import com.slack.api.util.json.GsonFactory;
+import org.junit.jupiter.api.Test;
+
+public class DataTableTest {
+    @Test
+    public void testExample01() {
+        DataTableBlock block = DataTable.example01();
+        String actual = GsonFactory.createSnakeCase().toJson(block);
+        String expected = """
+            {
+              "type": "data_table",
+              "rows": [
+                [
+                  { "type": "raw_text", "text": "Item" },
+                  { "type": "raw_text", "text": "Count" }
+                ],
+                [
+                  { "type": "raw_text", "text": "Widgets" },
+                  { "type": "raw_number", "value": 42.0, "text": "42" }
+                ],
+                [
+                  { "type": "raw_text", "text": "Gadgets" },
+                  { "type": "raw_number", "value": 7.0, "text": "7" }
+                ]
+              ],
+              "caption": "Quarterly widget report",
+              "page_size": 10,
+              "row_header_column_index": 0
+            }
+            """;
+        assertEquals(JsonParser.parseString(expected), JsonParser.parseString(actual));
+    }
+}