JavaScript to provide links to all previous steps in installation assistant

In the installation assistant itself consider adding a “Timeline” on top, with clickable items so that we can jump to the last step directly if we want to, because for example, we already know that installation will take x hours and don’t care reading this twice.

My proposal is to add this on all pages: https://tails.boum.org/install/win/index.en.html, https://tails.boum.org/install/mac/index.en.html and https://tails.boum.org/install/debian/index.en.html

Something like step 1 - step 2 - step 3. Where the currently active step is visually distinguishable from the others.

Related issues

Related to #11269 (closed)

Original created by @u on 11495 (Redmine)

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