Custom rooms

[eliasku]

Add option to create room and share the link with friends. Custom room have various settings to create, for example:

• Name
• Max Players limit
• NPC spawn rate and limit

Unblocks:

• Co-op mode - players only fight versus NPC (to implement #39)
• Time-limit room option (to implement #49)

[3kh0]

The link could be something like https://13game.lol/#gamecode shellshockers uses this url scheme aswell.