Add whitespace/formatting automation to the build process

[lornajane]

Over time the formatting on our key documents has become inconsistent in terms of spacing and quotes, etc.

Add a tool to our build process for pull requests and the main branch to that that the official spec documents conform to our standards (as established by our current conventions).

[Bellangelo]

I have run some tests here and I have succeeded to format most of the cases using Prettier for formatitng and Markdownlint for linting. One thing that Prettier cannot catch is the optional quotes in the YAML properties and strings. There is an open issue for this case but couldn't find any solution to this.

[ralfhandl]

@lornajane Can this issue be closed?

The validate-markdown workflow now lints the published and work-in-progress spec documemts.

[lornajane]

Yes, I think so