Update DOCS for "Adding a new keyboard layout"

[frzsombor]

I've just created a pull request for adding Hungarian language with the proper keyboard layout and - of course - as I added Hungarian as a completely new language, I had to update/add more files that were described in the docs. However (as I only figured this out by debugging errors), I still think that the required modification of the following files are missing from the docs

• packages/keybr-keyboard/lib/load.ts and
• packages/keybr-keyboard/lib/data/layout.ts

And also

• It would be helpful to update the docs to describe how someone can easily import a layout from CLDR in packages/keybr-keyboard-generator/lib/index.ts
• And now, when someone adds a new layout, it is very likely that they have to also add a new language, so including a short tutorial for this would also be really helpful for future contributors. (Adding word list, generating Phonetic Model, etc. - for a quick reference anybody interested in how to do these in the latest version of the project, check my PR)