Fix example links

[jackfrosty908]

Example links were pointing to the master branch, which seems to not exist anymore.

Update these links to use main.

Before submitting this PR:

1. Make sure you are PR'ing from a fork, please do not push branches directly
   to this repository.
2. Ensure you've written sufficient tests for your work.
3. Double check that your changes will not break existing connectors (if
   applicable).
4. Double check that your changes do not break the react-search-ui-views
   storybook (if applicable).

Description

Example links were pointing to the master branch, which seems to not exist anymore.

List of changes

Updated README.md with new links

Associated Github Issues

#914

[cla-checker-service]

💚 CLA has been signed

[joemcelroy]

thanks for the PR! Could you sign the CLA and I will merge.

[jackfrosty908]

thanks for the PR! Could you sign the CLA and I will merge.

Ah whoops, should be signed now @joemcelroy