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/envcanada.js

@@ -138,7 +138,7 @@ WeatherProvider.register("envcanada", {
 	// being accessed. This is only pertinent when using the EC data elements that contain a textual forecast.
 	//
 	getUrl() {
-		return "https://dd.weather.gc.ca/citypage_weather/xml/" + this.config.provCode + "/" + this.config.siteCode + "_e.xml";
+		return `https://dd.weather.gc.ca/citypage_weather/xml/${this.config.provCode}/${this.config.siteCode}_e.xml`;
 	},
 
 	//