Better and clearer documentation for RustDesk OpenSource Server.

[filu34]

Right now whole documentation is a mess, and lacks many crucial informations. I did all steps from there and strill can't result in properly working hbbs server, that connects with a clients.

Make better documentation.

[soekmego]

To add some constructive points, especially for the pro version since we are going to use rustdesk commercially and already have orders on the table:

Env vars
I followed the documentation on the website for the pro version yet could not find any traces of possible env vars until I opened up GitHub. Having the env var matrix available in the docs would have saved me a little bit of time. Default values would have been nice too.

Ports
On the OSS install page the ports are listed nicely (even 21114 which is not required for the OSS version), on the Pro version page they are missing.

Search
I think the documentation page is lacking a search function.

I cant think of anything else right now but will add new comments as soon as I stumble upon something.