feat: add task_card block example

Add example for the experimental task_card block type which displays
a single task with status, output, and sources.

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

Author: zimeg

block-kit/src/blocks/task_card.py

@@ -0,0 +1,43 @@
+from slack_sdk.models.blocks import RichTextBlock, TaskCardBlock
+from slack_sdk.models.blocks.block_elements import (
+    RichTextElementParts,
+    RichTextSectionElement,
+    UrlSourceElement,
+)
+
+
+def example01() -> TaskCardBlock:
+    """
+    Displays a single task which represents a single action.
+    This is an experimental block type that requires a toggle to preview.
+    https://docs.slack.dev/reference/block-kit/blocks/task-card-block/
+
+    A task card with output and sources.
+    """
+    block = TaskCardBlock(
+        task_id="task_1",
+        title="Fetching weather data",
+        status="pending",
+        output=RichTextBlock(
+            elements=[
+                RichTextSectionElement(
+                    elements=[
+                        RichTextElementParts.Text(
+                            text="Found weather data for Chicago from 2 sources"
+                        )
+                    ]
+                )
+            ]
+        ),
+        sources=[
+            UrlSourceElement(
+                url="https://weather.com/",
+                text="weather.com",
+            ),
+            UrlSourceElement(
+                url="https://www.accuweather.com/",
+                text="accuweather.com",
+            ),
+        ],
+    )
+    return block

block-kit/tests/blocks/test_task_card.py

@@ -0,0 +1,41 @@
+import json
+
+from src.blocks import task_card
+
+
+def test_example01():
+    block = task_card.example01()
+    actual = block.to_dict()
+    expected = {
+        "type": "task_card",
+        "task_id": "task_1",
+        "title": "Fetching weather data",
+        "status": "pending",
+        "output": {
+            "type": "rich_text",
+            "elements": [
+                {
+                    "type": "rich_text_section",
+                    "elements": [
+                        {
+                            "type": "text",
+                            "text": "Found weather data for Chicago from 2 sources",
+                        }
+                    ],
+                }
+            ],
+        },
+        "sources": [
+            {
+                "type": "url",
+                "url": "https://weather.com/",
+                "text": "weather.com",
+            },
+            {
+                "type": "url",
+                "url": "https://www.accuweather.com/",
+                "text": "accuweather.com",
+            },
+        ],
+    }
+    assert json.dumps(actual, sort_keys=True) == json.dumps(expected, sort_keys=True)