Update readme

[erikyo]

After the recent updates we should mention some additional information about the package update script and about the i18n files generation:

• Since we are using this script to sync the dependencies to a specific version of Gutenberg we should add the link to that table so, that way one can decide the target version of your plugin
• A brief explanation of how the i18n module that creates pot files works @wordpress/babel-plugin-makepot