Prevent adding extra `/` when concatenating locale paths (#2665)

* Formatting the locales pathname to be more accurate

Before this change, the URL would refer
`https://localhost//static/locales/${locale}.json`
which technically works in most web browsers,
but it does not work in Cordova at all, so this
changes the links to be more accurately:
`https://localhost/static/locales/${locale}.json`

* Removing usage of `path` because it requires a polyfill/shim

* Linting the code

src/renderer/i18n/index.js

@@ -60,7 +60,7 @@ class CustomVueI18n extends VueI18n {
         }
 
         if (url.pathname) {
-          url.pathname += `/static/locales/${locale}.json`
+          url.pathname += `${!url.pathname.endsWith('/') ? '/' : ''}static/locales/${locale}.json`
         } else {
           url.pathname = `/static/locales/${locale}.json`
         }