ADMIN: Add people to tags (GSoC)

[meetulr]

Is your feature request related to a problem? Please describe.

Implements the UI to add people to tags, i.e. assigning the tag to people.

Describe the solution you'd like.

A modal that would let us select the users and then assign them the tag.

Additional context

This is a companion issue of the one in the admin PalisadoesFoundation/talawa-api#2552

[meetulr]

Please assign it to me.

[github-actions]

This issue did not get any activity in the past 10 days and will be closed in 180 days if no update occurs. Please check if the develop branch has fixed it and report again or close the issue.