Update MongoDB in documentation

[Esa Jokinen]

The documentation for Standard Installation says:

MongoDB wth Ubuntu 22.04, need to have libssl1.1 installed.

echo “deb http://security.ubuntu.com/ubuntu impish-security main” | sudo tee /etc/apt/sources.list.d/impish-security.list sudo apt-get update sudo apt-get install libssl1.1

That's because MongoDB 4.4 from 2020 is advised to be used. I'm currently running all the tests within #1066 using:

• mongodb-org 7.0.7 https://www.mongodb.com/evolved#mdbsevenzero
• libssl3:amd64 3.0.2-0ubuntu1.15

If a more recent MongoDB 7.x was used, there wouldn't be the dependency for libssl1.1 & the impish-security repository.

[Esa Jokinen]

Things led to others and during rebuilding the entire html documentation from .rst I ended up improving the documentation building process, too. There might still be some minor inconsistencies or out-of-date instructions, but overall it should now better match the current state of the project.