V3: enable option to hide/expand tab content on click

[sanchosk]

Describe the Web Server enhancement

Currently, when sensors are grouped to "tabs", there is the option to double-click to expand the width.
I would like to have the option to click on the tab header 1x and have it to show/hide its content.
Also, in the YAML for the tab configuration (sorting_groups), it would be great to have configuration option such as "content_shown" that would default to true, but would allow me to enter false and start the webpage with such tab hidden.
Also, to make the visual style correct, when the tab content is hidden, the header needs to have CSS display set to block, otherwise the headers will "pile up" :)

Use cases

When I have a specific tab for detailed configuration of motion sensor and I don't want to see all the parameters, I would click the header and the whole tab would hide, only the tab header would stay.

Visual examples (optional)

Hidden content:

Shown content: