[SPARK-33264][SQL][DOCS] Add a dedicated page for SQL-on-file in SQL documents

### What changes were proposed in this pull request?

This PR intends to add a dedicated page for SQL-on-file in SQL documents.
This comes from the comment: https://github.com/apache/spark/pull/30095/files#r508965149

### Why are the changes needed?

For better documentations.

### Does this PR introduce _any_ user-facing change?

<img width="544" alt="Screen Shot 2020-10-28 at 9 56 59" src="https://user-images.githubusercontent.com/692303/97378051-c1fbcb80-1904-11eb-86c0-a88c5269d41c.png">

### How was this patch tested?

N/A

Closes #30165 from maropu/DocForFile.

Authored-by: Takeshi Yamamuro <yamamuro@apache.org>
Signed-off-by: Takeshi Yamamuro <yamamuro@apache.org>

docs/_data/menu-sql.yaml

@@ -175,6 +175,8 @@
                   url: sql-ref-syntax-qry-select-hints.html
                 - text: Inline Table
                   url: sql-ref-syntax-qry-select-inline-table.html
+                - text: File
+                  url: sql-ref-syntax-qry-select-file.html
                 - text: JOIN
                   url: sql-ref-syntax-qry-select-join.html
                 - text: LIKE Predicate

docs/sql-ref-syntax-qry-select-file.md

@@ -0,0 +1,76 @@
+---
+layout: global
+title: File
+displayTitle: File
+license: |
+  Licensed to the Apache Software Foundation (ASF) under one or more
+  contributor license agreements.  See the NOTICE file distributed with
+  this work for additional information regarding copyright ownership.
+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+ 
+     http://www.apache.org/licenses/LICENSE-2.0
+ 
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+---
+
+### Description
+
+You can query a file with a specified format directly with SQL.
+
+### Syntax
+
+```sql
+file_format.`file_path`
+```
+
+### Parameters
+
+* **file_format**
+
+    Specifies a file format for a given file path, could be TEXTFILE, ORC, PARQUET, etc.
+
+* **file_path**
+
+    Specifies a file path with a given format.
+
+### Examples
+
+```sql
+-- PARQUET file
+SELECT * FROM parquet.`examples/src/main/resources/users.parquet`;
++------+--------------+----------------+
+|  name|favorite_color|favorite_numbers|
++------+--------------+----------------+
+|Alyssa|          null|  [3, 9, 15, 20]|
+|   Ben|           red|              []|
++------+--------------+----------------+
+
+-- ORC file
+SELECT * FROM orc.`examples/src/main/resources/users.orc`;
++------+--------------+----------------+
+|  name|favorite_color|favorite_numbers|
++------+--------------+----------------+
+|Alyssa|          null|  [3, 9, 15, 20]|
+|   Ben|           red|              []|
++------+--------------+----------------+
+
+-- JSON file
+SELECT * FROM json.`examples/src/main/resources/people.json`;
++----+-------+
+| age|   name|
++----+-------+
+|null|Michael|
+|  30|   Andy|
+|  19| Justin|
++----+-------+
+```
+
+### Related Statements
+
+* [SELECT](sql-ref-syntax-qry-select.html)

docs/sql-ref-syntax-qry-select.md

@@ -85,7 +85,7 @@ SELECT [ hints , ... ] [ ALL | DISTINCT ] { named_expression [ , ... ] }
      * [Table-value function](sql-ref-syntax-qry-select-tvf.html)
      * [Inline table](sql-ref-syntax-qry-select-inline-table.html)
      * Subquery
-     * [File](sql-data-sources-load-save-functions.html#run-sql-on-files-directly)
+     * [File](sql-ref-syntax-qry-select-file.html)
      
 * **PIVOT**
 
@@ -165,6 +165,7 @@ SELECT [ hints , ... ] [ ALL | DISTINCT ] { named_expression [ , ... ] }
 * [Common Table Expression](sql-ref-syntax-qry-select-cte.html)
 * [Hints](sql-ref-syntax-qry-select-hints.html)
 * [Inline Table](sql-ref-syntax-qry-select-inline-table.html)
+* [File](sql-ref-syntax-qry-select-file.html)
 * [JOIN](sql-ref-syntax-qry-select-join.html)
 * [LIKE Predicate](sql-ref-syntax-qry-select-like.html)
 * [Set Operators](sql-ref-syntax-qry-select-setops.html)

docs/sql-ref-syntax-qry.md

@@ -39,6 +39,7 @@ ability to generate logical and physical plan for a given query using
   * [Common Table Expression](sql-ref-syntax-qry-select-cte.html)
   * [Hints](sql-ref-syntax-qry-select-hints.html)
   * [Inline Table](sql-ref-syntax-qry-select-inline-table.html)
+  * [File](sql-ref-syntax-qry-select-file.html)
   * [JOIN](sql-ref-syntax-qry-select-join.html)
   * [LIKE Predicate](sql-ref-syntax-qry-select-like.html)
   * [Set Operators](sql-ref-syntax-qry-select-setops.html)

docs/sql-ref-syntax.md

@@ -56,6 +56,7 @@ Spark SQL is Apache Spark's module for working with structured data. The SQL Syn
    * [HAVING Clause](sql-ref-syntax-qry-select-having.html)
    * [Hints](sql-ref-syntax-qry-select-hints.html)
    * [Inline Table](sql-ref-syntax-qry-select-inline-table.html)
+   * [File](sql-ref-syntax-qry-select-file.html)
    * [JOIN](sql-ref-syntax-qry-select-join.html)
    * [LIKE Predicate](sql-ref-syntax-qry-select-like.html)
    * [LIMIT Clause](sql-ref-syntax-qry-select-limit.html)