FR: Notify volunteer of next slot being empty

[thibaultmol]

I had multiple scenario's where there wasn't anyone scheduled after me for the same task type in the same room.
In such a scenario that system should probably give a headsup to the volunteer or to the team to ask if the volunteer wants to do the next session as well.

[thibaultmol]

To add to this: being able to click 'next' to go right to the next task of the same type in the same location to see 'who', if anyone, is scheduled after you. would be nice