Add speaker tab to talk show page

[marcoroth]

This is not perfect yet, but this is a start with what I wanted to go for in #154.

[adrienpoly]

while it makes sense for talks having lots of speaker, this tab doesn't really add any value for most talks as the majority of the talks have only one speaker.

I wonder if displaying the speakers bellow the title as we do on the card wouldn't be enough

[marcoroth]

Yeah, maybe we could do it inline if there is one speaker or otherwise add the speaker tab

[marcoroth]

I think it still makes sense to have the speakers tab for the case where there are a lot of speakers. But now I made it so that clicking on the "See all speakers" reveals the speakers tab with all the speakers.