docs: add 11.x to 12.x changelog and update TOC

Add missing changelog entry for the 11.x to 12.x migration, which
includes the removal of config object cloning (breaking change),
tedious 19 upgrade, and rfdc removal. Also add missing 10.x and 9.x
changelog entries to the table of contents.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dhensby

README.md

@@ -186,6 +186,9 @@ const config = {
 * [Data Types](#data-types)
 * [SQL injection](#sql-injection)
 * [Contributing](https://github.com/tediousjs/node-mssql/wiki/Contributing)
+* [11.x to 12.x changes](#11x-to-12x-changes)
+* [10.x to 11.x changes](#10x-to-11x-changes)
+* [9.x to 10.x changes](#9x-to-10x-changes)
 * [8.x to 9.x changes](#8x-to-9x-changes)
 * [7.x to 8.x changes](#7x-to-8x-changes)
 * [6.x to 7.x changes](#6x-to-7x-changes)
@@ -2217,6 +2220,13 @@ request.query('select @myval as myval', (err, result) => {
 })
 ```
 
+## 11.x to 12.x changes
+
+- Config objects are no longer cloned by the library. Mutating a config object after passing it to a `ConnectionPool` results in undefined behaviour.
+- Removed `rfdc` dependency
+- Upgraded to tedious version 19
+- Upgraded `@tediousjs/connection-string` to 0.6.x
+
 ## 10.x to 11.x changes
 
 - Upgraded to tedious version 18