[proposal] Add suggestion for logo upload

The logo uploaded from Portal will be displayed in various pages (/membership/exploreMembership.php, and eventually members section of all working groups' websites).

So, to have a good and clean visual effect, it's important our members upload the logo in a proper format.

I think a recommended logo format is no/small margin around.

Some bad examples I found:

, big margin around the logo (white area)

, huge margin bottom (transparent area)

And some good examples:

, no margin

, small margin

This is how they look like on the page (https://sdv.eclipse.org/index.html#members):

I am thinking we can add suggestion on org profile page on Portal. Can be added under current instructions:

Something like: "To better display the logo across Eclipse Foundation websites, please upload a version without too much margin unless it's part of it."

I don't think every member will notice this suggestion and upload what we recommend, but at least we do what we can atm.

WDYT? //cc @sgiacomoni2as @cguindon @malowe