Embed map into event info

[dct0]

Basic Information

• Add a new optional field to the event model called location_url. This will be a google maps link that can be pasted
• Add this field to the new event form. Use a simple regex to validate the url
• Embed the map link as an iframe on the single event page

Other Information

[Are there any additional information that we should know about?]

[github-actions[bot]]

Branch issue-74-Embed_map_into_event_info created!