Discuss template engine

[ludovicm67]

Try to use something like handlebars as a template engine instead of our custom solution to avoid any issue.

[bergos]

We agreed in the call 2022-07-04:

• handlebars will be the default template engine
• all plugins will use handlebars but will bring their own instance
• it should be possible to configure the default template engine but this can be done later in a separate step
• should be documented in the wiki