docs: add Azure Firewall scrape (#64)

Author: locmai

docs/scraping/providers/azure-firewall.md

@@ -0,0 +1,37 @@
+---
+tags:
+  - Scraper
+  - Resource Discovery
+  - Azure Firewall
+---
+
+# Azure Firewall
+
+![Availability Badge](https://img.shields.io/badge/Available%20Starting-v2.12-green.svg)![Resource Discovery Support Badge](https://img.shields.io/badge/Support%20for%20Resource%20Discovery-Yes-green.svg)
+
+You can scrape an Azure Firewall via the `AzureFirewall`
+ resource type.
+
+When using declared resources, the following fields need to be provided:
+
+- `azureFirewallName` - The name of the Azure Firewall.
+
+All supported metrics are documented in the official [Azure Monitor documentation](https://learn.microsoft.com/en-us/azure/azure-monitor/reference/supported-metrics/microsoft-network-azurefirewalls-metrics).
+
+## Example
+
+Here is an example configuration:
+
+```yaml
+name: azure_firewall_application_rule_hits
+description: number of times Application rules were hit	
+resourceType: AzureFirewall
+azureMetricConfiguration:
+  metricName: ApplicationRuleHit
+  aggregation:
+    type: Count
+  dimension:
+    name: Status
+resourceDiscoveryGroups:
+  - name: azure-firewalls
+```

mkdocs.yml

@@ -167,6 +167,7 @@ nav:
       - Azure Event Hubs: scraping/providers/event-hubs.md
       - Azure Express Route Circuit: scraping/providers/express-route-circuit.md
       - Azure File Storage: scraping/providers/file-storage.md
+      - Azure Firewall: scraping/providers/azure-firewall.md
       - Azure Front Door: scraping/providers/front-door.md
       - Azure Function App: scraping/providers/function-app.md
       - Azure IoT Hub Device Provisioning Service (DPS): scraping/providers/iot-hub-device-provisioning-service.md
@@ -222,6 +223,7 @@ nav:
       - Azure Event Hubs: scraping/providers/event-hubs.md
       - Azure Express Route Circuit: scraping/providers/express-route-circuit.md
       - Azure File Storage: scraping/providers/file-storage.md
+      - Azure Firewall: scraping/providers/azure-firewall.md
       - Azure Front Door: scraping/providers/front-door.md
       - Azure Function App: scraping/providers/function-app.md
       - Azure IoT Hub Device Provisioning Service (DPS): scraping/providers/iot-hub-device-provisioning-service.md