Rework PNG Icon with SVG and SCSS

[hswong3i]

Existing implementation using icon-fullscreen.png and icon-fullscreen-2x.png for different screen (e.g. iOS with retina display). Moreover, we don't have any toggle effect for the icon status.

This PR rework the icon with:

• Locally vendor Font Awesome v5.15.4 compress-solid.svg and expand-solid.svg
• Add default content for icon
• Add toggle status for icon
• Rework style with SCSS
• Create minified version JS and CSS
• Simplify demo and README.md with above changes

Some style reuse from: https://github.com/domoritz/leaflet-locatecontrol/pull/296

Online demo: https://drustack.github.io/brunob-leaflet.fullscreen/

Fix #87

Signed-off-by: Wong Hoi Sing Edison hswong3i@pantarei-design.com

[brunob]

Thx for the PR, really appreciate :) but i think this is an oversized code change for a small functional change. I'd like to :

• keep away from sass,
• don't provide a minified version (up to users to minify their sources with their chosen tools)

Anyway, i think the icon change on toggle is really needed change + the switch to a SVG icon (maybe we should use the one from https://github.com/Leaflet/Leaflet.fullscreen/blob/gh-pages/fullscreen.svg)

[hswong3i]

My similar PR: https://github.com/Leaflet/Leaflet.fullscreen/pull/118

My initial though are:

• Integrate this JS library with Drupal Leaflet module with an up-to-date implementation (since https://github.com/Leaflet/Leaflet.fullscreen looks non-active since 2018)
• Handle iOS fullscreen issue nicely
• Integrate together with https://github.com/domoritz/leaflet-locatecontrol for Drupal

BTW, I also face a critical issue here:

• When https://github.com/brunob/leaflet.fullscreen or https://github.com/domoritz/leaflet-locatecontrol working independently in demo, both always working well in both desktop or iOS browser (FF or Safari)
• When integrate these 2 JS library together, only desktop browser working; iOS FF or Safari are broken
• If integrate https://github.com/domoritz/leaflet-locatecontrol with https://github.com/Leaflet/Leaflet.fullscreen, all working well...

Sorry that I will shift my focus back to using https://github.com/Leaflet/Leaflet.fullscreen (even it is inactive, I could using my patched version for my client project, now).