Feat: Add default_response option in plugin-survey-likert

[ethanknights]

Hi

To save time in certain paradigms, I found myself wanting to add a default response to Likert values -

This PR proposes to add the default_response optional argument so that scale values are pre-selected.

A couple of tests around this are added & are passing in npm test with jest.

[changeset-bot]

🦋 Changeset detected

Latest commit: 55121f7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@jspsych/plugin-survey-likert	Minor

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[jadeddelta]

hi @ethanknights , thank you so much for the contribution! we really appreciate it, almost everything is in order. before merging, i'm going to add a changeset so that we can properly version and release this out under a minor version, because it is a backwards-compatible feature! for future reference, you can run npm run changeset in the root directory to add a changeset and the CLI will guide you through the steps of adding one.