Improve documentation for newcomers

[AntonOfTheWoods]

There are lots of bits of doc that are obsolete or no longer valid. A great example is https://github.com/yrutschle/sslh/blob/master/doc/INSTALL.md?plain=1#L110 , which says to use basic.cfg as a starting point. This file has not been updated in 3 years, and has invalid values (like verbose: 0). This file is also referenced at the top of example.cfg https://github.com/yrutschle/sslh/blob/master/example.cfg#L4 as being a better base for someone to use, even though example.cfg is up to date and basic.cfg isn't.

All this makes compiling and getting things running much, much more difficult than it should be for newcomers.

I can definitely help to improve this but will need some guidance and help to sanity check any changes! My idea for this ticket was to get some guidance or suggestions from maintainers, and then propose some changes.

[yrutschle]

Go for it, this kind of feedback is extremely valuable and the timing is perfect to fix documentation before v2.0.
I did try to update the documentation a bit, but I guess I'm too far in the code to see what's wrong with it :-)

I simplified basic.cfg majorly to make it an actual minimal basic configuration, rather than a mix between basic and documentation.

Feel free to point out what you see as wrong, propose PRs, whatever

[poVoq]

Would be interesting if it is possible to do SNI routing based on wildcard domains, like sending all requests with example.com or *.example.com to one server.

I was trying to do the same with my OPNsense router and it seems impossible to configure that way.