Update README.md (#90)

This pull request updates the installation instructions in the
`README.md` file to provide platform-specific guidance for Windows and
MacOS users.

Documentation improvements:

*
[`README.md`](diffhunk://#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5L14-R23):
Added separate installation instructions for Windows and MacOS,
including a prerequisite step for MacOS users to install OpenSSL before
using `pip` to install `mssql-python`.

Author: sumitmsft

README.md

@@ -11,10 +11,16 @@ The driver is compatible with all the Python versions >= 3.10
 > 
 ## Installation
 
-mssql-python can be installed with [pip](http://pypi.python.org/pypi/pip)
+**Windows:** mssql-python can be installed with [pip](http://pypi.python.org/pypi/pip)
 ```bash
 pip install mssql-python
 ```
+**MacOS:** mssql-python can be installed with [pip](http://pypi.python.org/pypi/pip)
+```bash
+brew install openssl
+pip install mssql-python
+```
+
 ## Key Features
 ### Supported Platforms
 
@@ -103,4 +109,4 @@ This project may contain trademarks or logos for projects, products, or services
 trademarks or logos is subject to and must follow 
 [Microsoft's Trademark & Brand Guidelines](https://www.microsoft.com/en-us/legal/intellectualproperty/trademarks/usage/general).
 Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship.
-Any use of third-party trademarks or logos are subject to those third-party's policies.
+Any use of third-party trademarks or logos are subject to those third-party's policies.