Introduce vale linter and improve standards

[gingerwizard]

For checking prose we want to explore introducing Vale .

Other work here includes:

• no external links (md file links only)
• consistent capitalization of word list e.g. ClickHouse
• enforce SSL links on external sites (checking of links is under new link checker work)

@DamianMaslanka5 has suggested rules created by GitLab.