fix(types): Mark defaultValue arguments required

[andersk]

Why am I submitting this PR

It seems these arguments are always provided to the defaultValue function. (This doesn’t prevent the function from ignoring them: for example, { defaultValue: () => "hello" } still satisfies this type.)

Does it fix an existing ticket?

No

Checklist

• [x] only relevant code is changed (make a diff before you submit the PR)
• [x] do no modify the version in package.json or CHANGELOG.md
• [ ] tests are included and pass: yarn test (see details here)
• [ ] documentation is changed or added

[adrai]

fyi: https://github.com/i18next/i18next-parser/issues/1148