Add in @-ms-viewport and @-o-viewport to CSS grammar

[jpcastberg]

Requirements

• Filling out the template is required. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• All new code requires tests to ensure against regressions

Description of the Change

Adds support for vendor prefixes -ms- and -o- to the viewport at-rule

Alternate Designs

No alternatives considered, I think I have fixed it appropriately within the architecture.

Benefits

Css grammar support will reflect viewport syntax used in older browsers.

Possible Drawbacks

...none?

Applicable Issues

fixes #176

[jpcastberg]

looking for a maintainer to take a look... @sadick254 ?