tgui: ESLint and VSCode settings improvements (#57905)

Added column 80 rulers to all javascript and scss files.
    Added a "prettier" config to have sensible defaults for those who prefer to use it.
    Added RadarJS (fork of SonarQube's SonarJS). Launchable only via bin/tgui --lint-harder for now.
    Disabled ESLint rule for parens around arrow function arguments, because in TypeScript they're pretty much always required, and I don't want to replace it throughout the codebase.
    Removed unused javascript extensions from tooling (jsx, mjs).

.vscode/settings.json

@@ -20,5 +20,14 @@
 	],
 	"files.eol": "\n",
 	"gitlens.advanced.blame.customArguments": ["-w"],
-	"tgstationTestExplorer.project.resultsType": "json"
+	"tgstationTestExplorer.project.resultsType": "json",
+	"[javascript]": {
+		"editor.rulers": [80]
+	},
+	"[typescript]": {
+		"editor.rulers": [80]
+	},
+	"[scss]": {
+		"editor.rulers": [80]
+	}
 }