Add guide for screego

[no-one]

Fixes #1799

[no-one]

A question for the person who will review this pull request later: I have not currently entered a port range for the TURN server. There is the following example in the config:

# Limit the ports that TURN will use for data relaying.
# Format: min:max
# Example:
#   50000:55000
SCREEGO_TURN_PORT_RANGE=

In most cases this will probably not be so relevant (because STUN can be used instead of TURN) but if this is not the case: As you can see, a fairly large range is specified. However, ports can only be opened individually. What do you suggest?

[nichtmax]

A question for the person who will review this pull request later: I have not currently entered a port range for the TURN server. There is the following example in the config:

# Limit the ports that TURN will use for data relaying.
# Format: min:max
# Example:
#   50000:55000
SCREEGO_TURN_PORT_RANGE=

In most cases this will probably not be so relevant (because STUN can be used instead of TURN) but if this is not the case: As you can see, a fairly large range is specified. However, ports can only be opened individually. What do you suggest?

I wouldn't bother. The documentation states: "While STUN should work for most cases, there are stricter NATs f.ex. Symmetric NATs where it doesn’t, then, TURN will be used."

How about an info box with a link to their documentation? 5000 Ports is a bit excessive, I don't know what's the minimum range, maybe ask them? ☺️

[nichtmax]

Thanks for your guide! I left you some comments, I'll test everything when these are resolved.