Support for data-* attributes in Gutenberg blocks

Add support for data-* attributes in Gutenberg blocks. Currently, adding data-* attributes to any element via the code editor results in an error message saying “Block contains unexpected or invalid content”.

data-* attributes are needed by thousands of websites because they help them leverage hundreds of features and design changes.

One small example. Using the data-nosnippet HTML attribute in Google’s recommendations for hiding elements in search engine results (SEO)

https://developers.google.com/search/docs/crawling-indexing/robots-meta-tag#data-nosnippet-attr