pkgdown organization + vignette

[sigmafelix]

• Vignette revision
• Vignette 3 (par_* examples) removed
• pkgdown content organization

[codecov[bot]]

Codecov Report

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

Comparison is base (09b8aad) 99.17% compared to head (0ccf254) 99.17%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #52 +/- ## ======================================= Coverage 99.17% 99.17% ======================================= Files 5 5 Lines 603 603 ======================================= Hits 598 598 Misses 5 5 ```

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