This commit introduces the documentation link widget, the aim is to
standardize the help documentation links that can be found in the views.
This widget will add an icon (o_doc_link), this icon is a link to the
documentation. Note that you can use relative or absolute path. The
relative path is relative to `https://www.odoo.com/documentation/server_version`,
so it's not necessary to hard-code the server version on the arch any more.
```xml
<widget name="documentation_link" documentation="/applications/technical/web/settings/this_is_a_test.html"/>
```
Task-id: 2980478
Part-of: odoo/odoo#110432
Jorge Pinna Puissant
80e1c0062e