Template XONTRIBS_AUTOLOAD_DISABLED conflict with other xontribs and type conflicts

[eugenesvk]

The template suggests disabling autoloading via
$XONTRIBS_AUTOLOAD_DISABLED = {"ptk_shell", }

There are a few of issues with this:

• It would override the same variable set by other xontribs instead of appending
• From the docs, the type of XONTRIBS_AUTOLOAD_DISABLED could either by a bool or a list, but you use a set, so actually appending this variable becomes a challenge due to a difference in updating lists and sets

[jnoortheen]

Closing as the PR is merged already.

[eugenesvk]

The PR only addresses the last point, not the first two

[jnoortheen]

Now the readme is updated