Accessibility Issues on Leaflet markers and popups

[peteredwards]

WCAG Criterion 2.1.1 Keyboard (Level A)

• Cannot always navigate to the close button on the map dot modals via keyboard. Particularly after a group of dots has been clicked on.
• Unable to open grouped map dots via keyboard.

WCAG Criterion 2.4.3 Focus Order (Level A)

• Focus doesn't move to the map popups triggered by selecting the markers
• Cannot close the map popups via keyboard that open after selecting a map dot with keyboard
• Cannot determine whether focus is returned to the marker after the popup has closed

[peteredwards]

I've updated both Leaflet and the markerclusterer plugin as I noticed there was some movement in these projects on issues with keyboard access to clusters and moving focus to popups. I'll try to get these issues re-tested