Add language localisation

[jameshball]

Osci-render should support different major languages to increase accessibility.

JUCE's LocalisedStrings class is designed for this, and https://forum.juce.com/t/application-for-creating-juce-translation-files/9092 could help create the translation files.

Rather than using an English string to map, we should use camelCase names to map the strings so that the string used to map doesn't take up lots of space in the source code. We want to keep this complexity in the translation files themselves.