ref: enhance code readability

[GuiLeme]

What does this PR do?

This PR does several things:

• Refactors the code to separate a bit better the responsibilities and enhance code readability with that;
• Fix minor layout/UI issues (such as the sidekick panel's input when focused);
• Fix wrong behaviour of open the type captions panel in everyone's UI (moderators);

Motivation

This PR will increase readability and maintainability of this plugin and also fix some minor issues

More

This PR is still in draft because there are still a couple of things left to do regarding refactor, but first, it needs 2 fixes in the CORE:

• bug: Multiple subchannels in defferent places won't update bigbluebutton-html-plugin-sdk#236;
• bug: sidekick content throws error when panel is set to open bigbluebutton-html-plugin-sdk#237;