Custom elements based theme switcher

	## How to

		### Define theme in your CSS:
		.theme-blue-yellow {
			--primary-color: #33cccc;
			--secondary-color: #cccc33;
			--background-color: #051414;
		}

		### Add this custom element to your HTML

		<theme-switch
			themes="theme-blue-yellow theme-dark-silver theme-deep-purple" default="theme-blue-yellow"
			key="my-themes">
			<button id="theme-switch" onclick="parentNode.dispatch()">Toggle Theme</button>
		</theme-switch>


		### Add your way of saving the theme name to preserve it on next page load

		themeSwitch.addEventListener('theme-change', function onThemeChange(event) {
			// change the theme and save current theme as state to localStorage to backend etc.
			// replace default function with your own
			this.switch((themeName) => localStorage.setItem('andromeda-web', themeName));
		});