Rename peakdet to prep4phys

[tsalo]

Closes none.

Proposed Changes

• Rename peakdet to prep4phys throughout the site.
• Fix link to prep4phys contributors list.
• Update .gitignore to ignore built site folder and .DS_Store files.

Change Type

• bugfix
• refactoring
• infrastructure
• documentation
• other

Checklist before review

• I added everything I wanted to add to this PR.
• [Documentation only] I built the docs locally.
• My contribution is harmonious with the rest of the code: I'm not introducing repetitions.
• My code respects the adopted style, especially linting conventions.
• The title of this PR is explanatory on its own, enough to be understood as part of a changelog.
• I added or indicated the right labels.

• I added information regarding the timeline of completion for this PR.

• Please, comment on my PR while it's a draft and give me feedback on the development!