[DialogHelper] Multiselect : added an option to the "select" function that makes the possibility of multiselect options.

When the option list appears, you can select more than one value separated by comma.

 Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        |