Add React component examples for Dropdown to website

[alisonjoseph]

Add React examples to website for Dropdown. (see current site for examples https://www.carbondesignsystem.com/components/dropdown/code) Could use codesandbox plugin for this.

• [x] Multiselect Dropdown
• [x] Inline Multiselect Dropdown
• [x] Filter Dropdown

[joshblack]

• MultiSelect: https://codesandbox.io/s/50739oq2lx
• Inline MultiSelect: https://codesandbox.io/s/zq9o7l4543
• Filterable MultiSelect: https://codesandbox.io/s/ovx9j0rkq9
• Combobox: https://codesandbox.io/s/kkrnjj5vx7

[joshblack]

cc @mattrosno any tips for using these in Gatsby with the codesandbox plugin?

[alisonjoseph]

@mattrosno can you sync up with Josh so we can get these added this week 🙏

[mattrosno]

@alisonjoseph @joshblack just seeing this. I'll submit a PR to get working codesandboxes in there, separate from tutorial PR.

Not sure how good the embedded codesandboxes would look in there... sure we don't want to simply link out to React Storybook like how it's handled in v9 components?

[alisonjoseph]

v9 has those components directly on the page, I suppose we could do the same, just might be a little more work to get them in there

[alisonjoseph]

Oh, for examples above, should we switch to experimental v10 versions for the next site?

[asudoh]

@alisonjoseph Good point - Created #1057 for that.

[asudoh]

Oh sorry NVM I had a wrong assumption that we put the React components directly to <ComponentExample>.

[asudoh]

Created experimental styled version at: #1058

[asudoh]

Created #1059 just in case more direct live demo (like vanilla ones) is more desirable.