Handle special characters in rtn req. bookmarks

https://eaflood.atlassian.net/browse/WATER-4685

> Part of the work to migrate managing return requirements from NALD to WRLS

In [Add site description to rtn. req. bookmark links](#1358) we added the return requirement site description to the bookmarks we display when viewing a return version with more than one requirement.

However, in that change we didn't cater for the fact users have added site descriptions that include special characters, for example `& " '`.

When these descriptions are included in the bookmark links, they appear like this.

- `Return reference 100234 - Quantities taken between points X, Y &Z`
- `Return reference 100432 - Opposite "Old cottage" entrance`
- `Return reference 100567 - Borehole in 'middle' field`

This changes updates the logic to escape these characters.