README file updates

[vv-monsalve]

Hi @josescaglione, @casasin

This PR updates the Readme file of the repo. It includes:

• [x] Formatting edits to make each section more clear
• [x] Build instructions update
• [x] Design variation axes small adjustmens
• [x] Font model name schema explanation
• [x] Font model name fixes plus the display name added to the table

@simoncozens. Please review the## Build instructions and check if the CI build information is ok. Please feel free to make adjustments to this PR.

@casasin, @josescaglione, please review the sections ## Country recipes and ## Create or edit handwriting models a detailed review to update them as necessary.

[vv-monsalve]

Closing this since it's bringing a long list of unwanted files