feat(generic-content): allow injecting generic content in the sidekick panel

[Arthurk12]

What does this PR do?

This PR implements the feature to allow injecting generic content to the sidekick panel. Specifically, this PR:

• Renames all occurrences of 'generic-component' to 'generic-content'
• Adds 2 types of 'generic-content':
  1. MAIN_CONTENT: Displayed over the presentation area
  2. SIDEKICK_CONTENT: Displayed in the sidekick panel when the associated button is clicked
• Maps the already existing generic-component to generic-content of type MAIN_CONTENT
• Ensures that each injected generic sidekick content is automatically associated with a button in the navigation sidebar to toggle its panel.
• Adds a simple sample showcasing how to use the generic sidekick content

HTML5 related part: https://github.com/bigbluebutton/bigbluebutton/pull/20463

What is still missing?

• Grouping navigation sidebar buttons of generic contents by section name.
• Enabling/disabling the three dots in the top right corner of the panel, as well as injecting buttons.

Closes

Closes #76