Localization of Aerial's UI (On hold pending next macOS release)

**Edit : Just a heads up for everyone, I'm putting the UI stuff on hold until the next macOS release is announced. Currently Catalina has broken localization for screensavers and I can't workaround that bug ! We still translate video names though so if you like to help with that for another language, let us know !**

Hi everyone,

With version 1.4.8, we already started a pretty important translation effort, thanks to @aitor. As of 1.5.0, we have translations for all video names, and all our custom descriptions in:

- English (original text) by @SeanMSmith
- Spanish by @aitor
- French by @glouel
- Polish by @Soruk
- German by @moeffju
- Hebrew by @kaaspad
- Arabic by @kachikulu
- Simplified Chinese by @LinkeyLeo

Following the release of 1.5.0, I'll be working on making Aerial's UI translatable. This should be fairly straightforward, using a `Localizable.strings` that we can import in [Lokalise](https://lokalise.co/) so everyone can work on their language.

This will probably take a few days for me to setup so if you are interested to give a hand with the translation in a language (you don't need to know anything about programming), keep an eye on this issue (I'll keep it pinned) or let us know in comments below which language you want to help with (I'll do french ;)) !

The same goes if you would like to help translate video names and descriptions in a language not mentionned above, let us know in this issue and @aitor or I will get you setup for this.

Thanks all!

Review the issue thread and the planned Localizable.strings import into Lokalise; the UI localization work is explicitly on hold because Catalina breaks screensaver localization. Confirm whether the next macOS release removes that blocker, then define the UI strings to translate and verify that localized video names and descriptions remain supported.

Written by the indexing model from the issue text.