feat(jsx-email): add Conditional (mso) component

[shellscape]

Component / Package Name: jsx-email

This PR contains:

• [ ] bugfix
• [x] feature
• [ ] refactor
• [ ] documentation
• [ ] other

Are tests included?

• [x] yes (bugfixes and features will not be merged without tests)
• [ ] no

Breaking Changes?

• [ ] yes (breaking changes will not be merged unless absolutely necessary)
• [x] no

If yes, please include "BREAKING CHANGES:" in the first commit message body, followed by a description of what is breaking.

List any relevant issue numbers:

Description

This PR adds a new Conditional component to the project which renders conditional HTML comments such like

<!--[if mso]> ... <![endif]-->