Could you add a header slot to the popover and other calcite components that are similar? Currently I use a calcite label with dynamic scale using the header slot so that the header changes size with the rest of the components. This is a very convenient way to perform this task using React. I realize there is a heading level, however, when most other calcite components use a scale system ('s'|'m'|'l'), it is better for me to stick to that standard.