#661 Issue - Add first version for new visualisation Vignette

[nikosbosse]

Description

This PR closes #661

For the upcoming scoringutils release, we dropped a few plotting functions that were hard to maintain and not very general. We decided moving that code to a dedicated Vignette. In a future issue, we should address more visualisations that could go into a separate Vignette.

The PR:

• creates a vignette draft
• copies in old function code into the vignette with examples
• adds a news item
• adds Visualisations.Rmd to the files ignored by the lintr. This is because the file uses ::: which the lintr doesn't like and complains about
• adds ggdist as a suggest in DESCRIPTION - This is because the Vignette requires it and CI checks on gh actions fail without it

Instead of adding ggdist to suggests, we could also modify the code in the Vignette. But then it would be a slightly different function that behaves differently.

Checklist

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

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.28%. Comparing base (ce8720b) to head (a0887ab).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #711 +/- ## ======================================= Coverage 95.28% 95.28% ======================================= Files 21 21 Lines 1632 1632 ======================================= Hits 1555 1555 Misses 77 77 ```

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