Offline search no longer works under Bootstrap v5

[chalin]

I tried to figure out what might be broken. I think it is because the usage has changed, compare:

• https://getbootstrap.com/docs/5.3/components/popovers/#usage
• https://getbootstrap.com/docs/4.6/components/popovers/#usage

At a minimum, the JS file will need to be udpated:

• https://github.com/google/docsy/blob/main/assets/js/offline-search.js

[chalin]

@tekezo or @deining - might either of you be willing to work on this?

[chalin]

@tekezo et al.: I've made an update for the arrow class name:

• [BSv5] Offline-search adjust arrow class name #1427

But I think that it might be necessary to change the template further. For example, maybe popover-body needs to be renamed to popover-inner? As I mentioned in the PR, for details, see:

• The template entry of https://getbootstrap.com/docs/5.3/components/popovers/#options.

[tekezo]

Offline search starts working partially with my local commits.
I'll make PR later.

[tekezo]

@chalin I created PR for offline search updates for Bootstrap v5.
Please review it!
#1429