title: Use multiSubnetFailover in sequelize and mssql packages
body: <p>I have a backend application (Node.JS) that uses mssql (v7) and sequelize (v6) npm packages.</p>
  <p>Since my production DB configuration is (and can be only) accessed by an AGL, hence I need to set <code>multisubnetfailover=true</code> in the DB connection string.</p>
  <p>Although support for this existed in previous versions, I am unable to find the same in the current stable versions of the respective packages. (Here's a sample code for previous <a href="https://github.com/tediousjs/tedious/pull/362#issuecomment-307885255" rel="nofollow noreferrer">sequelize</a> and <a href="https://github.com/tediousjs/node-mssql/issues/640#issue-313014675" rel="nofollow noreferrer">mssql</a> version)</p>
  <p>Is there a way to enable this in the newer version?</p>