Parse matrix.to URLs in Explore rooms input field to extract room alias

**Is your suggestion related to a problem? Please describe.**
I use Element-web in messenger aggregators (Ferdi, Rambox, etc), which can't register the `matrix://` protocol or catch `matrix.to` domain links.

So opening URL like https://matrix.to/#/#matrix-stand:fosdem.org?web-instance[element.io]=chat.fosdem.org
is little tricky:

For open this URL I must manually find and extract the room alias `#matrix-stand:fosdem.org` from it, and paste into "Explore rooms" dialog's input field, for got the "Join" button.

**Describe the solution you'd like**
Will be good if Element automatically detect `matrix.to` links in "Explore rooms" dialog's input field and show the "Join" button.