Translating Arduino-IDE using Theia's nls API

[msujew]

Hi team,

this PR adds translation keys for all user-facing strings inside of the Arduino-IDE using the Theia localization (nls) API.

Be aware that this does not add actual translations for the app. However, some strings are nevertheless translated, as they are contained by the vscode language pack.

How to test

0. Start the app and observe that all user-facing strings are still correct (in English)
1. Download a language pack of your choice from the vscode marketplace/ovsx registry.
2. Unzip it and place it into the plugins folder
3. Start the application and run the Configure Display Language command and change to your new language
4. Open the File menu.
5. Observe that some menu entries have been changed.

[CLAassistant]

All committers have signed the CLA.

[silvanocerza]

Great jobs! It works really well and without issue. Approving. 👍

[fstasi]

@msujew the labels that are not translated are those coming from theia, is this assumption correct?

[msujew]

@fstasi Yes and no. Those coming from Theia are not translated (as the appropriate PR isn't merged yet), as well as those that are specifically for your app (nls ids starting with arduino/*), since the Transifex pipeline isn't in place yet.

The only ones that are currently translated are the ones that are specified inside of the arduino-ide (like close/open/exit/etc.) but exist inside of the vscode language packs.