Search rooms inside a space ("explore rooms")

### Your use case

Note: Im not a programmer, just someone who would like a feature, please

#### What would you like to do?
Element classic had the functionality to search a room inside a space called "explore rooms".

#### Why would you like to do it?
We are using matrix as university internal communication. As there are many lectures, we have 400+ rooms inside a space which is impossible to go through by hand.

This is the large feature we need, to be able tu use element X on a large scale. So it is somethin we desperately need!

#### How would you like to achieve it?
By implementing it again :)

### Have you considered any alternatives?

Maybe automatic alphabetic ordering of rooms when viewing the space-overview?

### Additional context

Dont know what a PR is, so I clicked "no"

### Are you willing to provide a PR?

No