Add some ESLint rules + minor changes (#3665)

Main point was to enable ESLint `dot-notation` and `no-unneeded-ternary`
rules for more code consistency.

I took the occasion to add two minor commits:
- Fix a problem found by running `test:spelling
- Minor dependency update

It wouldn't be a problem if the PR didn't arrive in the next release,
the changes are cosmetic.

js/electron.js

@@ -102,7 +102,7 @@ function createWindow () {
 	 */
 
 	let prefix;
-	if ((config["tls"] !== null && config["tls"]) || config.useHttps) {
+	if ((config.tls !== null && config.tls) || config.useHttps) {
 		prefix = "https://";
 	} else {
 		prefix = "http://";
@@ -151,11 +151,11 @@ function createWindow () {
 	//remove response headers that prevent sites of being embedded into iframes if configured
 	mainWindow.webContents.session.webRequest.onHeadersReceived((details, callback) => {
 		let curHeaders = details.responseHeaders;
-		if (config["ignoreXOriginHeader"] || false) {
+		if (config.ignoreXOriginHeader || false) {
 			curHeaders = Object.fromEntries(Object.entries(curHeaders).filter((header) => !(/x-frame-options/i).test(header[0])));
 		}
 
-		if (config["ignoreContentSecurityPolicy"] || false) {
+		if (config.ignoreContentSecurityPolicy || false) {
 			curHeaders = Object.fromEntries(Object.entries(curHeaders).filter((header) => !(/content-security-policy/i).test(header[0])));
 		}