Refactoring HTML anatomy of items in layers

[Anshpreet8]

Used the svg "More Vert" icon instead of the details element to avoid having to nest interactive elements inside the summary element, as the suggested layout in the proposal for alternative layer item anatomy

Closes #263

[ahmadayubi]

Was there a reason for using SVG for icons rather than HTML Icons? In terms of lines of code using HTML icons would reduce SVG generation to a single line of code simply assigning the icon value.

An example of how HTML icons are used can be seen here:
https://github.com/Maps4HTML/Web-Map-Custom-Element/blob/14375f26c641a03c74cb798856d63a9c232caa27/src/mapml/control/ReloadButton.js#L10

[Anshpreet8]

Was there a reason for using SVG for icons rather than HTML Icons? In terms of lines of code using HTML icons would reduce SVG generation to a single line of code simply assigning the icon value.

An example of how HTML icons are used can be seen here:

https://github.com/Maps4HTML/Web-Map-Custom-Element/blob/14375f26c641a03c74cb798856d63a9c232caa27/src/mapml/control/ReloadButton.js#L10

The suggestion to use svg icons was made #263

[ahmadayubi]

I get the following error in my console, in case you haven't come across this already, it's a present error in all the files I've checked so far: