Use template literals instead of string concatenation (#3066)

We have used it inconsistently till now. Template literals are more
modern and easier to maintain in my opinion.

Because that's a large amount of changes, here's a way to reproduce it:
I added the rule `"prefer-template": "error"` to the `.eslintrc.json`
and did an autofix. Since this caused a new problem in line 409 of
`newsfeed.js`, I reversed it in that line and also removed the rule from
the eslint config file.

The rule is described here:
https://eslint.org/docs/latest/rules/prefer-template

Note: I've played around with some other linter rules as well, and some
seem to point to some specific, non-cosmetic, issues. But before I dive
even deeper and then introduce even bigger and hardly understandable
changes at once, I thought I'd start with this simple cosmetic rule.

modules/default/weather/providers/openmeteo.js

@@ -264,9 +264,9 @@ WeatherProvider.register("openmeteo", {
 				switch (key) {
 					case "hourly":
 					case "daily":
-						return encodeURIComponent(key) + "=" + params[key].join(",");
+						return `${encodeURIComponent(key)}=${params[key].join(",")}`;
 					default:
-						return encodeURIComponent(key) + "=" + encodeURIComponent(params[key]);
+						return `${encodeURIComponent(key)}=${encodeURIComponent(params[key])}`;
 				}
 			})
 			.join("&");