Extensible areas: Action button dropdown

[GuiLeme]

Feature request

As discussed in the BBB world conference, the idea here is to bring the Action button dropdown to be an extensible area as well.

See target area on image bellow:

Following the steps of the whiteboard toolbar extensible area, we have to define what properties are we going to send to the html5 client in order for it to correctly interpret the component that it has to mount, and also, we need to specify what possible components is the extensible area going to support (just like the whiteboard toolbar button and the spinner).

Properties and supported components:

Components:

• Button;
• Information (non-interactive menu);

The last one would be some information on the presentation such as how many presentation does this meeting have, how many slides are annotated, and things like that.

Properties:

For the base component:

interface ActionButtonDropdownItem {
  label: string,
  icon: string,
  tooltip: string,
}

For the Information:

class ActionButtonDropdownInformation implements ActionButtonDropdownItem {
  label: string,
  icon: string,
  tooltip: string,
  type: string,
}

For the Button:

class ActionButtonDropdownButton implements ActionButtonDropdownItem{
  label: string,
  icon: string,
  tooltip: string,
  type: string,
  onClick: () => void,
  allowed: boolean,
}

Those are just schemes for us to base ourselves on, it can change along the way. Any other suggestions, feel free to comment them out.