docs: add ClickHouse and Elasticsearch loggers. (#7848)

README.md

@@ -135,6 +135,8 @@ A/B testing, canary release, blue-green deployment, limit rate, defense against
   - [Fault Injection](docs/en/latest/plugins/fault-injection.md)
   - [REST Admin API](docs/en/latest/admin-api.md): Using the REST Admin API to control Apache APISIX, which only allows 127.0.0.1 access by default, you can modify the `allow_admin` field in `conf/config.yaml` to specify a list of IPs that are allowed to call the Admin API. Also, note that the Admin API uses key auth to verify the identity of the caller. **The `admin_key` field in `conf/config.yaml` needs to be modified before deployment to ensure security**.
   - External Loggers: Export access logs to external log management tools. ([HTTP Logger](docs/en/latest/plugins/http-logger.md), [TCP Logger](docs/en/latest/plugins/tcp-logger.md), [Kafka Logger](docs/en/latest/plugins/kafka-logger.md), [UDP Logger](docs/en/latest/plugins/udp-logger.md), [RocketMQ Logger](docs/en/latest/plugins/rocketmq-logger.md), [SkyWalking Logger](docs/en/latest/plugins/skywalking-logger.md), [Alibaba Cloud Logging(SLS)](docs/en/latest/plugins/sls-logger.md), [Google Cloud Logging](docs/en/latest/plugins/google-cloud-logging.md), [Splunk HEC Logging](docs/en/latest/plugins/splunk-hec-logging.md), [File Logger](docs/en/latest/plugins/file-logger.md), [SolarWinds Loggly Logging](docs/en/latest/plugins/loggly.md))
+  - [ClickHouse](docs/en/latest/plugins/clickhouse-logger.md): push logs to ClickHouse.
+  - [Elasticsearch](docs/en/latest/plugins/elasticsearch-logger.md): push logs to Elasticsearch.
   - [Datadog](docs/en/latest/plugins/datadog.md): push custom metrics to the DogStatsD server, comes bundled with [Datadog agent](https://docs.datadoghq.com/agent/), over the UDP protocol. DogStatsD basically is an implementation of StatsD protocol which collects the custom metrics for Apache APISIX agent, aggregates it into a single data point and sends it to the configured Datadog server.
   - [Helm charts](https://github.com/apache/apisix-helm-chart)
   - [HashiCorp Vault](https://www.vaultproject.io/): Support secret management solution for accessing secrets from Vault secure storage backed in a low trust environment. Currently, RS256 keys (public-private key pairs) or secret keys can be linked from vault in [jwt-auth](docs/en/latest/plugins/jwt-auth.md#enable-jwt-auth-with-vault-compatibility) authentication plugin.