index.html Slider : add new image/link for 2021 meeting which should show as the default.

[christinerogers]

currently the default slider image on index.html is the 2020 GBC meeting. needs updating for 2021 meeting

@3design Would it be possible to see a draft of the slider image today (Thursday)?

• [x] make a new image for the GBC index.html Slider.
  Please make this the default slider image when globalbrainconsortium.org loads

background of image: use generic GBC image - e.g. This old Slider image is perfect as an example

Text: printed in the image

[GBC Logo centered] 2021 Annual Meeting November 22-23, 2021

And somewhere on the image:

Click for more info

• [x] Add a link on this slider image -- upon click, the page that should load is: event-annualMeeting-nov2021.html

• [x] Remove Varadero 2020 Slider card. (it was lovely, sad to see it go)

[christinerogers]

perfect. ready to go, pending jessica's review. merci encore.