Add multiselect feature to add people to lists

[nupuragrahari]

Currently the system allows adding one person to multiple lists.

For usability we need to make it possible for multiple people to be added to one list.

This would not be a replacement but an add on functionality.
On the List Detail Page

• show the people already present in it.
• make it possible to add more people to it.

[nupuragrahari]

@bind-ritu1211 to pick this up