Add a search bar to website

[olivroy]

Update pkgdown config.

Here is the new look

[olivroy]

@thomasp85, if you prefer, I can break this down in smaller PRs? and just add this to _pkgdown.yml in this one.

template:
  bootstrap: 5

[thomasp85]

Nah, this is fine - maybe just leave the DESCRIPTION file alone as that isn't relevant to this

[olivroy]

Done, thanks! I just left the Config/Needs/website: gifski as it is recommended to declare dependencies in DESCRIPTION rather than in GitHub actions.

[thomasp85]

Yes for sure - thanks a bunch!