Fix Themes v3 not working on Safari
Changes
Basically use <style>
elements to replace document.adoptedStyleSheets
if it is not available.
Note that this means that we are not able to use the advantage of the separation between eager and lazy styles.
In Safari I am also unable to clone the <style>
element and keep its sheet
property at the same time, so the style is modified in place.
Closes #1319 (closed)