feat(DropdownItem): Add support for .dropdown-item-text

[kyletsang]

• Bug fix
• New feature
• Chore
• Breaking change
• There is an open issue which this change addresses
• I have read the CONTRIBUTING document.
• My commits follow the Git Commit Guidelines
• My code follows the code style of this project.
• My change requires a change to the documentation.
• • I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

Adds support for plaintext menu items.

From Bootstrap docs:

You can also create non-interactive dropdown items with .dropdown-item-text. Feel free to style further with custom CSS or text utilities.

https://getbootstrap.com/docs/4.5/components/dropdowns/#menu-items

[kyletsang]

Hey @TheSharpieOne, unrelated side note, but if you’d like, I can help out with library maintenance. We still use this in my company, and I do want to make some improvements (possibly bring typescript defs in-house among other things).