v4.0.0-beta.0

Update for ajv v8
Support JSON Schema draft 2019-09
Support JSON Type Definition
Remove support for non-standard deprecated switch keyword
Add default error message
Rename Czech locale to cs

Thanks to @jmtoball, @lucacorti, @niekvb, @ggondim, @encX, @leuction, @minipai for the contributions of the translations for this version.