docs: add schemaless writing for cloud (#16801)

* docs: add schemaless writing for cloud

* docs: add section description and remove http from url

docs/en/07-data-in/05-rest-schemaless.md

+---
+sidebar_label: REST and Schemaless
+title: REST and Schemaless
+description: Insert data using REST API or Schemaless
+---
+
+<!-- exclude -->
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
+<!-- exclude-end -->
+
+In this section we will explain how to write into TDengine cloud service using REST API or schemaless protocols over REST interface.
+
+## REST API
+
+### Config
+
+Run this command in your terminal to save the TDengine cloud token and URL as variables:
+
+<Tabs defaultValue="bash">
+<TabItem value="bash" label="Bash">
+
+```bash
+export TDENGINE_CLOUD_TOKEN="<token>"
+export TDENGINE_CLOUD_URL="<url>"
+```
+
+</TabItem>
+<TabItem value="cmd" label="CMD">
+
+```bash
+set TDENGINE_CLOUD_TOKEN="<token>"
+set TDENGINE_CLOUD_URL="<url>"
+```
+
+</TabItem>
+<TabItem value="powershell" label="Powershell">
+
+```powershell
+$env:TDENGINE_CLOUD_TOKEN="<token>"
+$env:TDENGINE_CLOUD_URL="<url>"
+```
+
+</TabItem>
+</Tabs>
+
+### Insert Data using REST API
+
+Following command below show how to insert data into the table `d1001` of the database `test` via the command line utility `curl`.
+
+```bash
+curl -L \
+  -d "INSERT INTO d1001 VALUES (1538548685000, 10.3, 219, 0.31)" \
+  $TDENGINE_CLOUD_URL/rest/sql/test?token=$TDENGINE_CLOUD_TOKEN
+```
+
+## Schemaless
+
+### InfluxDB Line Protocol
+
+You can use any client that supports the http protocol to access the RESTful interface address `<cloud_url>/influxdb/v1/write` to write data in InfluxDB compatible format to TDengine. The EndPoint is as follows:
+
+```text
+/influxdb/v1/write?db=<db_name>&token=<cloud_token>
+```
+
+Support InfluxDB query parameters as follows.
+
+- `db` Specifies the database name used by TDengine
+- `precision` The time precision used by TDengine
+
+Note: InfluxDB token authorization is not supported at present. Only Basic authorization and query parameter validation are supported.
+
+### OpenTSDB Json and Telnet Protocol
+
+You can use any client that supports the http protocol to access the RESTful interface address `<cloud_url>/opentsdb/v1/put` to write data in OpenTSDB compatible format to TDengine. The EndPoint is as follows:
+
+```text
+/opentsdb/v1/put/json/<db>?token=<cloud_token>
+/opentsdb/v1/put/telnet/<db>?token=<cloud_token>
+```