Add documentation how to properly install or use custom OpenSSL version

[Franky1]

I refer to the section OpenSSL in the README.md

• Is this custom OpenSSL version still required?
• If i follow the link to the other github repo, it seems to be not maintained anymore?
• Will the systems default openssl version work too?

If this custom OpenSSL version is still required: Maybe it is a no brainer for experienced Linux users, but please add or fix the install description in the section OpenSSL I tried it in a fresh Ubuntu 18.04 in Virtualbox, but couldn't get this to work properly. Some dependencies are missing?

sudo apt-get install build-essential --yes
sudo apt-get install libz-dev --yes

And after running the installation commands openssl version -a still points to the default openssl version that was pre-installed on the system.

[tomato42]

Is this custom OpenSSL version still required?

yes

If i follow the link to the other github repo, it seems to be not maintained anymore?

it's not so much unmaintained as it's hard to move to 1.1.x branch

Will the systems default openssl version work too?

yes, but then it won't show support for ciphers unsupported by systems' default openssl version

see also: #165 and #118

Maybe it is a no brainer for experienced Linux users, but please add or fix the install description in the section OpenSSL I tried it in a fresh Ubuntu 18.04 in Virtualbox, but couldn't get this to work properly. Some dependencies are missing?

there's an already-compiled copy included in this repo, use it

And after running the installation commands openssl version -a still points to the default openssl version that was pre-installed on the system.

you absolutely shouldn't install the custom openssl system-wide, you should build it statically and use that statically-built binary, if you have problems compiling it, please refer to its documentation