created button variant for error with white text

[heejung-hong]

Fixes #1929

What changes did you make?

• Changed warning buttons with red background to have white text instead of black.
• Changed CSV Download button styles per style guide.
• Changed Share Snapshot button styles per style guide.

Why did you make the changes (we will use this info to test)?

• UX Research recommended the changes after testing with users.

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Screenshots of Proposed Changes Of The Website (if any, please do not screen shot code changes)

Visuals before changes are applied

Visuals after changes are applied