fix(skip-link): add to exports (#320)

I'd like to add skip links from the DSR to the `sbl-frontend` project,
but we're currently not exporting them.

## Changes

- adds an export for skip links

## How to test this PR

1. Can you now import skip links from the DSR?

## Screenshots

![Screenshot 2024-03-18 at 4 43 50
PM](https://github.com/cfpb/design-system-react/assets/19983248/9ad951e4-f8a3-472e-aa13-aff01bcb8786)

## TODO
- there are some additional focus styles that we might want to import
over later

src/index.ts

@@ -44,6 +44,7 @@ export { RadioButton } from './components/RadioButton/RadioButton';
 export { Select } from './components/Select/Select';
 export { SelectMulti } from './components/Select/SelectMulti';
 export { SelectSingle } from './components/Select/SelectSingle';
+export { default as SkipNav } from './components/SkipNav/SkipNav';
 export { Table } from './components/Table/Table';
 export { Tagline } from './components/Tagline/Tagline';
 export { TextArea } from './components/TextInput/TextArea';