[Docs] Add network flows that should be authorized

[fl42]

Hello,

Some users would like to restrict network flows, but currently it's hard to determine which flow should be authorized.
Therefore, keeping a list of remote services (URLs) required for Teslamate is useful.

Furthermore, blocking network traffic leads to error messages that are not obviously related to network.
For instance, if streaming API is not reachable, Teslamate logs are:

2024-05-09 15:58:15.849 car_id=1 [info] Start / :online
2024-05-09 15:58:15.907 car_id=1 [info] Connecting ...
2024-05-09 15:58:16.197 car_id=1 [info] Start / :online
2024-05-09 15:58:16.233 car_id=1 [info] Connecting ...
2024-05-09 15:58:16.583 car_id=1 [info] Start / :online
2024-05-09 15:58:16.636 car_id=1 [info] Connecting ...
2024-05-09 15:58:16.940 car_id=1 [info] Start / :online
2024-05-09 15:58:16.979 car_id=1 [info] Connecting ...
2024-05-09 15:58:17.427 car_id=1 [info] Start / :online
2024-05-09 15:58:17.440 car_id=1 [info] Connecting ...
2024-05-09 15:58:17.780 car_id=1 [info] Start / :online
2024-05-09 15:58:17.818 car_id=1 [info] Connecting ...

And PostgreSQL logs are:

ERROR:  canceling statement due to user request

Log messages don't allow straightforward identification of the root cause (but this is to be improved in another PR ;) )

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