Add support for SQL Server

[bradcypert]

Is your feature request related to a problem? Please describe.
I'd love to be able to run deckard migrations against MS SQL Server.

Describe the solution you'd like
Deckard can leverage an existing popular SQL Server library (see below) to performa operations against SQL Servers.
https://github.com/denisenkom/go-mssqldb

Describe alternatives you've considered
Not using SQL Server 🤷‍♂

Additional context
Flagging this as a "Good First Issue" despite the name being intimidating, this issue shouldn't be too difficult as the way Deckard handles database operations is relatively tame. If you want to pick this one up and have questions, lemme know. I'd be happy to help answer those. :)