Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

This table is not relevant for several install methods (Vagrant/Docker/Generic).

For Ubuntu/Debian, I think it's useful information, but it's a bit
overwhelming, and what we're basically doing is elaborating on a couple
words (*it needs to be a __recent__, supported version of Ubuntu/Debian -
which is specifically yadda yadda...*).

If one is oblivious to this content and runs the install script on an
unsupported version of Ubuntu/Debian, that should be safe -- since the first
thing it does is to verify compatibility.

Note: not trying to bury - the next commit will call this out a bit more.

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

This makes the new section match the other sections.

It seems to me like  "Create the default payment processor file" should be the first subheading under "Setup"

This contains a mix of typo and style fixes, removes some bits that
were copied from APIv3 and adds some missing sections.

The extension name is just `myextension`, not `com.example.myextension`.

See https://chat.civicrm.org/civicrm/channels/dev-newcomers

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>

Co-Authored-By: Mikey O'Toole <mikey@mjco.uk>