Add session/speaker social sharing cards

[abraham]

Generate 2:1 images for sessions/speakers that are good to share on Twitter.

Info to include:

• speaker name
• speaker image
• session title
• conference logo
• date
• conference url
• conference location
• ~conference name?~
• ~speaker title?~
• ~hashtag~

How to handle sessions with multiple speakers? How to handle speakers with multiple sessions? Needs to handle long and short text.

Examples:

• https://twitter.com/gdevdc/status/1134112485345288192?s=20
• https://twitter.com/RefactrTech/status/1133389222319202304?s=20
• https://twitter.com/RefactrTech/status/1133389222319202304?s=20
• https://twitter.com/GdGdallas/status/1095689232629317632?s=20
• https://twitter.com/DotProto/status/1158846027018858496?s=20
• https://twitter.com/symfony_live/status/1161253605510455297
• https://twitter.com/JSKongress/status/1161265405660487681?s=20
• https://twitter.com/honeypotio/status/1161579120540733440?s=20
• https://twitter.com/GdgTriangle/status/1166747575665475591
• https://twitter.com/devfestnantes/status/1153935915896778753

Implementation ideas:

• GDG has some prepared templates available for DevFest 2019.
• https://github.com/reverentgeek/undergroundjs-speaker-cards
• https://github.com/tsayen/dom-to-image
• https://htmlcsstoimage.com/

Sample implementation from DevFest WI: https://glitch.com/edit/#!/pleasant-whistle