Localize HeliosLauncher UI using lang files (#301)

* First step to use Language .json file in ejs

* i18n for landing.ejs

* i18n for login.ejs

* i18n for loginOptions.ejs

* i18n for overlay.ejs

* i18n for settings.ejs

* i18n for waiting.ejs

* i18n for welcome.ejs

* langloader.js placeholder support

* i18n for landing.js

* i18n for login.js

* i18n for overlay.js

* i18n for settings.js

* i18n for uibinder.js

* i18n for uicore.js

* remove html language replacement

* use toml for i18n

* Fix mojang/microsoft status icon is undefined

* cascadable langloader

* separate lang file for customization

* move some placeholder text to _placeholder.toml

* Update

* Reduce package lock diff.

* Remove another placeholder.

* Checkbox does not require translation.

* Icons don't need translation.

* Leave placeholders inline.

* Fix translation for news pages.

* Remove more unneeded translations.

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Co-authored-by: Daniel Scalzi <d_scalzi@yahoo.com>

app/assets/js/scripts/login.js

@@ -220,10 +220,7 @@ loginButton.addEventListener('click', () => {
         } else {
             // Uh oh.
             msftLoginLogger.error('Unhandled error during login.', displayableError)
-            actualDisplayableError = {
-                title: 'Unknown Error During Login',
-                desc: 'An unknown error has occurred. Please see the console for details.'
-            }
+            actualDisplayableError = Lang.queryJS('login.error.unknown')
         }
 
         setOverlayContent(actualDisplayableError.title, actualDisplayableError.desc, Lang.queryJS('login.tryAgain'))