xt-docs template changes

[nkrusch]

xt-docs command builds documentation site for an extension project using JSDoc3, which is quite useful for documentation purposes. The current default configuration uses a template called foodoc. But foodoc source is not being maintained, uses old packages, etc. so it is time to switch to something else.

Possible options (I would say in order of preference):

• find a different template that is being maintained
• fork foodoc template and start maintaining it
• make a new template
• default to default / no template

(I'm not able to find many that are being maintained) but here are some candidates:

• clean-jsdoc-theme
• Braintree JSDoc Template
• JSDoc Template
• tidy-jsdoc

Should also update the user guide and list all these options on there. A project can use any template they want. This issue is about choosing the default template.

EDIT: After trying some of these templates, not sure about using them. I am now thinking: set default to default in this project. Then fork foodocs and modify it (a lot) to update dependencies and the dated bootstrap style at which point is becomes a new-ish template. Add to the user guide a list of templates to use. So this is a mix of the last 3 options.