docs(mssql): add docs for source (#256)

Add docs for `mssql` source, and update for `mssql-sql` tool.

docs/en/resources/sources/mssql.md

@@ -0,0 +1,49 @@
+---
+title: "SQL Server"
+type: docs
+weight: 1
+description: >
+  SQL Server is a relational database management system (RDBMS).
+
+---
+
+##  About
+
+[SQL Server][mssql-docs] is a relational database management system (RDBMS)
+developed by Microsoft that allows users to store, retrieve, and manage large
+amount of data through a structured format.
+
+[mssql-docs]: https://www.microsoft.com/en-us/sql-server
+
+## Requirements
+
+### Database User
+
+This source only uses standard authentication. You will need to [create a
+SQL Server user][mssql-users] to login to the database with. 
+
+[mssql-users]: https://learn.microsoft.com/en-us/sql/relational-databases/security/authentication-access/create-a-database-user?view=sql-server-ver16
+
+## Example
+
+```yaml
+sources:
+    my-mssql-source:
+        kind: "mssql"
+        host: "127.0.0.1"
+        port: "1433"
+        database: "my_db"
+        user: "my-user"
+        password: "my-password"
+```
+
+## Reference
+
+| **field** | **type** | **required** | **description**                                                        |
+|-----------|:--------:|:------------:|------------------------------------------------------------------------|
+| kind      |  string  |     true     | Must be "mssql".                                                       |
+| host      |  string  |     true     | IP address to connect to (e.g. "127.0.0.1").                           |
+| port      |  string  |     true     | Port to connect to (e.g. "1433").                                      |
+| database  |  string  |     true     | Name of the SQL Server database to connect to (e.g. "my_db").          |
+| user      |  string  |     true     | Name of the SQL Server user to connect as (e.g. "my-user").            |
+| password  |  string  |     true     | Password of the SQL Server user (e.g. "my-password").                  |

docs/tools/mssql-sql.md

@@ -1,9 +1,10 @@
-# Cloud SQL Mssql Tool
+# SQL Server Tool
 
-A "mssql-sql" tool executes a pre-defined SQL statement against a Cloud SQL for SQL Server
+A "mssql-sql" tool executes a pre-defined SQL statement against a SQL Server
 database. It's compatible with any of the following sources:
 
 - [cloud-sql-mssql](../sources/cloud-sql-mssql.md)
+- [mssql](../sources/mssql.md)
 
 Toolbox supports the [prepare statement syntax][prepare-statement] of MS SQL
 Server and expects parameters in the SQL query to be in the form of either @Name