[docs/playground] show validation errors when buttons are disabled, allow sharing invalided schemas?

[toddbaert]

This is good, fixes the validation previously missing and good changes for the playground overall
Two things to note and add later

• schema validation feedback for the users when Evaluate or Share is disabled.
• allowing sharing of invalid schemas?

will be nice to improve the playground section, can be done in a separate PR/issue

Originally posted by @suthar26 in #1885 (review)

[suthar26]

you can assign me to this!