docs: create metadata page

docs/src/content/docs/docs/endpoints/metadata.mdx

@@ -0,0 +1,79 @@
+---
+title: Get metadata - /api/metadata
+---
+
+Currencies are identified by standard three-letter `ISO 4217` currency codes.
+
+import { Tabs, TabItem, Aside } from '@astrojs/starlight/components';
+
+## Get data on available dates and currencies.
+### Request
+
+<Tabs>
+    <TabItem label='Shell'>
+        <Tabs>
+            <TabItem label='curl'>
+```shell
+curl --request GET --url https://kekkai-api.redume.su/api/metadata/
+```
+            </TabItem>
+        </Tabs>
+    </TabItem>
+    <TabItem label='Python'>
+        <Tabs>
+            <TabItem label='requests'>
+```python
+import requests
+
+res = requests.get('https://kekkai-api.redume.su/api/metadata/', timeout=3)
+
+print(res.json())
+```
+            </TabItem>
+        </Tabs>
+    </TabItem>
+    <TabItem label='Node.JS'>
+        <Tabs>
+            <TabItem label='axios'>
+```javascript
+const axios = require('axios');
+
+axios.get('https://kekkai-api.redume.su/api/metadata/')
+    .then((res) => {
+        console.log(JSON.stringify(res.json()));
+    })
+    .catch((err) => {
+        console.error(err);
+    });
+```
+            </TabItem>
+        </Tabs>
+    </TabItem>
+</Tabs>
+
+### Response
+
+<Aside title='Output'>
+```json
+{
+    "first_date": "2024-11-26T21:00:00.000Z",
+    "last_date": "2025-01-01T21:00:00.000Z",
+    "currencies": {
+        "crypto": [
+            "USDT",
+            "TON",
+            "BTC",
+            "ETH"
+        ],
+        "fiat": [
+            "USD",
+            "RUB",
+            "EUR",
+            "UAH",
+            "TRY",
+            "KZT"
+        ]
+    }
+}
+```
+</Aside>