Added string Insert article

Author: waqasm78

docs2/pages/documentations/string/string-insert.md

@@ -0,0 +1,49 @@
+# String_Insert
+
+`String_Insert` returns a new string in which a `value` string is inserted at a specified index position in the `source` string.
+
+```csharp
+String_Insert (
+	@source NVARCHAR (MAX), 
+	@startIndex INT,
+	@value NVARCHAR (MAX)
+	)
+RETURNS NVARCHAR (MAX)
+```
+
+## Parameters
+
+  - **source**: The source string.
+  - **startIndex**: The zero-based index position of the insertion.
+  - **value**: The string to insert.
+
+## Returns
+
+A new string that is equivalent to the `source` string, but with `value` inserted at position `startIndex`.
+
+## Example
+
+```csharp
+SELECT SQLNET::String_Insert('This is a string.', 10, 'new ')
+SELECT SQLNET::String_Insert('aaaabbbb', 4, ' ')
+```
+
+# String_Insert4k
+
+It is equivalent to `String_Insert` except no NVARCHAR(MAX) parameters; it can be used when input data will never be over 4000 characters as this function offers better performance.
+
+```csharp
+String_Insert4k (
+	@source NVARCHAR (4000), 
+	@startIndex INT,
+	@value NVARCHAR (4000)
+	)
+RETURNS NVARCHAR (4000)
+```
+
+## Example
+
+```csharp
+SELECT SQLNET::String_Insert4k('This is a string.', 10, 'new ')
+SELECT SQLNET::String_Insert4k('aaaabbbb', 4, ' ')
+```