Vignette typos

[jcken95]

Description

This PR closes #969

• Fix mathematical error in interval coverage section
• Fix some spelling errors

Checklist

• My PR is based on a package issue and I have explicitly linked it.
• I have included the target issue or issues in the PR title as follows: issue-number: PR title
• I have tested my changes locally.
• I have added or updated unit tests where necessary.
• I have updated the documentation if required.
• I have built the package locally and run rebuilt docs using roxygen2.
• My code follows the established coding standards and I have run lintr::lint_package() to check for style issues introduced by my changes.
• I have added a news item linked to this PR.
• I have reviewed CI checks for this PR and addressed them as far as I am able.

• NOTE: linter failed, but unrelated to PR

[nikosbosse]

Ah sweet, thanks a lot for fixing this!

[jcken95]

No worries! Marking as ready despite failing pipeline - it's not related to this PR

[nikosbosse]

Yeah I've seen this linting error all morning. Happy to merge whenever you're ready!

[jackUKHSA]

yep, go ahead :)

[jackUKHSA]

I think this is the error btw RcppCore/Rcpp#1341

[nikosbosse]

Merging now. Thank you very much for your first contribution to scoringutils! If you feel like it, feel invited to add yourself as a contributor to the package. We're always happy about contributions!