Issue #3432293 by globexplorer: As a user I want to upload presentation slides to BBB

bigbluebutton.install

config/schema/bigbluebutton.schema.yml

src/BigBlueButtonHelper.php

src/Element/BigBlueButton.php

src/FieldHelper.php

src/LabelHelper.php

...in/Field/FieldFormatter/BigBlueButtonDefaultFormatter.php

src/Plugin/Field/FieldType/BigBlueButtonItem.php

src/Plugin/Field/FieldWidget/BigBlueButtonDefaultWidget.php

src/Utility/BigBlueButtonField.php

src/Utility/BigBlueButtonFormatHelper.php