Simplify exports for services, transitions and utils

[quentinderoubaix]

Context Currently our exports enforce users to import services, transitions and utils like the following:

import {createResizeObserver} from '@agnos-ui/svelte-bootstrap/services/resizeObserver';
// or
import {createResizeObserver} from '@agnos-ui/svelte-bootstrap';

We now judge thiat is a bit overkill and propose to separate only in main sub-areas, resulting in:

import {createResizeObserver} from '@agnos-ui/svelte-bootstrap/services';

Work involved

• [ ] update packages exports + add new index.ts in the required folders
• [ ] update internal imports (could be done automatically through the eslint plugin)
• [ ] potentially update the eslint plugin
• [ ] potentially update the script generateExports.js
• [ ] udpate the informative alert of the typedoc pages

[quentinderoubaix]

Requires further discussion, the Draft PR has not been deemed satisfiable yet.