accessibility bugs wave 1

[YingXue]

Accessibility fixes:

1. Announce button click
2. Annouce search result
3. Move hyper link css to global
4. Properly style input placeholder text globally
5. Remove unused color from palatte
6. Copy code from Portal's Copy button implementation

General Guidelines

• [x] If introducing new functionality or modified behavior, are they backed by unit tests?
• [x] Have all unit tests passed locally? (by running npm run test command)
• [x] Have you updated the README.md with new screenshots if significant changes have been made?
• [x] Have you update the package version if the current version in package.json is not higher than the version released?