Mg/dropdown

[whymarlene]

Description

Closes #52

Adds dropdown component

Type of change

🆕 Feature

How to Test

Run yarn storybook and click on dropdown component in the website.

https://user-images.githubusercontent.com/61206258/141388476-9d56e4cf-d16c-469f-a640-925f41bc3548.mov

Checklist

• [x] Code follows design and style guidelines
• [x] Code is commented with doc blocks
• [x] Latest code has been rebased from base branch (usually develop)
• [x] Commits follow guidelines (concise, squashed, etc)
• [x] Github issues have been linked in relevant commits
• [x] Relevant reviewers (EM) have been assigned to this PR

[therealsharath]

Temporary fix for the radio buttons. Checkbox needs further rework so opened a new issue. @lilyyang606 @alysonlam the dev side, for now, seems to be done. If everything other than the checkbox type dropdown looks good, then I'd go ahead and approve this PR.

[alysonlam]

also looks good to me :) I'll go ahead and approve this